Adam Dugdale scored the only goal of the game to give Crewe the advantage over Southend after the first leg of the League Two play-off semi-final.
Centre-half Dugdale headed home Ashley Westwood's free-kick early in the second half to ruin the Shrimpers' run of five successive clean sheets.
A fine save by visiting keeper Cameron Belford denied AJ Leitch-Smith another.
But Southend had chances, Steve Phillips saving from Michael Timlin, before Bilel Mohsni headed just over.
Crewe, now unbeaten in 17 games, were worthy winners over Southend, who arrived at Gresty Road in impressive form having won four of their last five matches.
And the Alex once again did it without captain David Artell, who, having missed three games with hamstring trouble, was forced out because of a broken bone in his foot sufffered in training on Thursday.
Crewe showed first on a sun-kissed evening in Cheshire, with Matt Tootle almost getting on the end of a Byron Moore cross, while teenage top scorer Nick Powell was crowded out in the box after some clever footwork.
Southend struggled to test Phillips in the first half but Ryan Hall had a shot blocked soon after the restart as they began with greater intent.
But it was Crewe who grabbed the lead when Westwood launched a free-kick into the visitors' box and Dugdale looped a header over Belford.
The visiting keeper then superbly pushed Leitch-Smith's effort over the bar before his side finally found their feet in the final 20 minutes.
Phillips had to parry well when Mohsni cushioned a header into the path of Timlin, before Mohsni, who scored three of his 13 league goals this season in Southend's leageu double over the Alex, headed over at the far post.
There was still time for Hall to drive wide from 20 yards but Crewe held on to ensure they take a lead to Roots Hall on Wednesday night (16 May, 1945 BST).
VIEW FROM THE DRESSING ROOM
Crewe Alexandra manager Steve Davis told BBC Radio Stoke:
"It was a big contest today between experience and youth.
"Five or six of this team are in their first season in professional football and they've coped very well. We were mindful of Mohsni's threat in the air and that worked.
"But now we've got to do it all again down there and that's going to be very hard. And Southend will be wounded.
"We've got to be ready for what they throw at us on Wednesday night."
- 01 Phillips
- 02 Tootle
- 03 Davis
- 06 Dugdale
- 15 Martin Booked (Bodin - 89' )
- 04 Westwood
- 08 Murphy (Bell - 77' )
- 17 Mellor
- 10 Leitch-Smith (Clayton - 84' )
- 11 Moore
- 25 Powell
- 13 Martin
- 07 Bell
- 34 Bodin
- 09 Miller
- 19 Clayton
- 35 Belford
- 02 Clohessy
- 03 Gilbert
- 06 Bilel
- 15 Phillips (Prosser - 66' )
- 23 Barker
- 04 Hall Booked
- 07 Grant
- 08 Timlin
- 12 Ferdinand (Leonard - 60' )
- 09 Harris (Eastwood - 73' )
- 01 Morris
- 16 Prosser
- 18 Leonard
- 24 Benyon
- 37 Eastwood
Live Text Commentary
Full Time The referee ends the match.90:00 +3:25
The ball is delivered by Anthony Grant, Freddy Eastwood has an effort at goal from deep inside the area missing to the right of the target.90:00 +2:31
Sean Clohessy fouled by Byron Moore, the ref awards a free kick. Cameron Belford restarts play with the free kick.90:00 +1:56
Bilel Mohsni challenges Lee Bell unfairly and gives away a free kick. Free kick taken by Kelvin Mellor.90:00 +1:01
The ball is swung over by Billy Bodin, Luke Prosser makes a clearance.90:00 +0:37
Corner taken by Ashley Westwood played to the near post, save made by Cameron Belford.89:39
Free kick awarded for an unfair challenge on Ashley Westwood by Luke Prosser. Kelvin Mellor restarts play with the free kick.88:37 Substitution
Substitution (Crewe) makes a substitution, with Billy Bodin coming on for Carl Martin.85:21
Ryan Hall takes a shot. Steve Phillips makes a fantastic save. Inswinging corner taken by Ryan Hall from the right by-line played to the near post, save made by Steve Phillips.83:13 Substitution
Substitution Max Clayton comes on in place of Ajay Leitch-Smith.80:46
Foul by Anthony Grant on Nick Powell, free kick awarded. Ashley Westwood restarts play with the free kick.79:23
Peter Gilbert challenges Ashley Westwood unfairly and gives away a free kick. Ashley Westwood takes the free kick.78:29
The ball is sent over by Ryan Hall, Close range header by Bilel Mohsni goes over the crossbar.77:49
Matt Tootle produces a cross, Peter Gilbert makes a clearance.76:30
Free kick taken by Steve Phillips.76:30 Substitution
Substitution Lee Bell replaces Luke Murphy.76:30
The referee blows for offside.74:29
Luke Murphy challenges Anthony Grant unfairly and gives away a free kick. Free kick taken by Ryan Hall.72:30
Cameron Belford takes the free kick.72:30 Substitution
Substitution Freddy Eastwood is brought on as a substitute for Neil Harris.
The referee blows for offside.71:58
The ball is swung over by Ryan Leonard, save by Steve Phillips.70:17
Ryan Leonard delivers the ball, Michael Timlin takes a shot. Steve Phillips makes a save.69:05
Matt Tootle fouled by Ryan Leonard, the ref awards a free kick. Direct free kick taken by Ashley Westwood.67:58
Anthony Grant sends in a cross.67:41
Ajay Leitch-Smith sends in a cross, Chris Barker makes a clearance.65:32
Outswinging corner taken right-footed by Ashley Westwood, Ryan Leonard manages to make a clearance.65:32 Substitution
Substitution Luke Prosser on for Mark Phillips.65:32
Ajay Leitch-Smith takes a shot. Cameron Belford makes a save.64:56
Ryan Hall has shot on goal from just outside the box which goes wide of the right-hand upright.63:59
Shot from outside the box by Anthony Grant goes wide right of the target.63:02
The referee blows for offside. Cameron Belford restarts play with the free kick.61:31
Free kick awarded for an unfair challenge on Byron Moore by Anthony Grant. Direct free kick taken by Ashley Westwood.60:30
Shot from outside the penalty box by Matt Tootle goes wide right of the goal.59:35 Substitution
Substitution Ryan Leonard is brought on as a substitute for Kane Ferdinand.59:35
Peter Gilbert sends in a cross.58:13
Unfair challenge on Luke Murphy by Michael Timlin results in a free kick. Steve Phillips takes the direct free kick.56:06
The ball is delivered by Kelvin Mellor, Cameron Belford makes a save. Outswinging corner taken from the right by-line by Ashley Westwood, Nick Powell concedes a free kick for a foul on Ryan Hall. Free kick taken by Cameron Belford.55:16
Mark Phillips is caught offside. Steve Phillips takes the indirect free kick.55:03
A cross is delivered by Sean Clohessy, clearance by Carl Martin.53:29
Ashley Westwood takes the inswinging corner, Adam Dugdale produces a header from deep inside the six-yard box which goes wide of the right-hand post. Kane Ferdinand fouled by Ashley Westwood, the ref awards a free kick. Direct free kick taken by Michael Timlin.52:29
Ashley Westwood restarts play with the free kick.52:29 Booking
Booking Ryan Hall booked.52:14
Ryan Hall gives away a free kick for an unfair challenge on Nick Powell.51:14
Ryan Hall crosses the ball from the free kick left-footed from left wing, Kelvin Mellor manages to make a clearance.51:14 Booking
Booking Booking for Carl Martin for unsporting behaviour.51:06
Foul by Carl Martin on Peter Gilbert, free kick awarded.50:39
Anthony Grant fouled by Luke Murphy, the ref awards a free kick. Free kick taken by Cameron Belford.48:52
Assist on the goal came from Ashley Westwood.48:52 Goal scored
Goal! - Adam Dugdale - Crewe 1 - 0 Southend Adam Dugdale finds the net with a headed goal from inside the six-yard box. Crewe 1-0 Southend.48:18
Chris Barker gives away a free kick for an unfair challenge on Nick Powell. Ashley Westwood restarts play with the free kick.47:47
The official flags Neil Harris offside. Steve Phillips takes the free kick.47:37
Ryan Hall produces a cross, Harry Davis makes a clearance.47:03
The ball is crossed by Ryan Hall.45:34
The assistant referee flags for offside against Nick Powell. Indirect free kick taken by Michael Timlin.45:01
The referee blows his whistle to start the second half.45:00 +2:16 Half time
Half Time The half-time whistle blows.45:00 +1:13
Sean Clohessy delivers the ball, Carl Martin makes a clearance. Neil Harris produces a cross, save by Steve Phillips.45:00 +0:43
Free kick awarded for an unfair challenge on Kane Ferdinand by Luke Murphy. Chris Barker takes the free kick.44:35
The ball is delivered by Peter Gilbert.43:33
Bilel Mohsni challenges Luke Murphy unfairly and gives away a free kick. The free kick is delivered right-footed by Ashley Westwood from left wing, clearance made by Anthony Grant.42:55
Nick Powell fouled by Bilel Mohsni, the ref awards a free kick. Direct free kick taken by Adam Dugdale.42:06
Effort from outside the penalty area by Luke Murphy goes wide left of the target.40:51
Centre by Ryan Hall, Kane Ferdinand produces a header from inside the area that goes over the bar.39:04
Headed effort from inside the area by Nick Powell misses to the right of the target.38:31
Free kick awarded for an unfair challenge on Byron Moore by Anthony Grant. Ashley Westwood takes the free kick.38:14
Centre by Neil Harris, clearance made by Adam Dugdale.37:17
Free kick awarded for a foul by Peter Gilbert on Ajay Leitch-Smith. Ashley Westwood takes the direct free kick.30:26
Foul by Neil Harris on Carl Martin, free kick awarded. Ashley Westwood takes the direct free kick.28:06
Corner taken right-footed by Ashley Westwood, Cameron Belford makes a save. Kelvin Mellor concedes a free kick for a foul on Cameron Belford. Free kick taken by Cameron Belford.26:55
The ball is crossed by Matt Tootle, save by Cameron Belford.26:03
Michael Timlin takes a shot. Comfortable save by Steve Phillips.25:13
A cross is delivered by Sean Clohessy.24:35
Ajay Leitch-Smith gives away a free kick for an unfair challenge on Ryan Hall. Cameron Belford takes the free kick.23:24
Mark Phillips gives away a free kick for an unfair challenge on Byron Moore. Shot comes in from Nick Powell from the free kick.22:13
Nick Powell delivers the ball, save made by Cameron Belford.21:28
Carl Martin crosses the ball, save by Cameron Belford.19:01
The ball is delivered by Sean Clohessy. Kane Ferdinand is ruled offside. Indirect free kick taken by Steve Phillips.18:07
Adam Dugdale gives away a free kick for an unfair challenge on Neil Harris. Free kick crossed left-footed by Ryan Hall, clearance made by Adam Dugdale.17:10
Luke Murphy concedes a free kick for a foul on Anthony Grant. Direct free kick taken by Cameron Belford.13:02
Unfair challenge on Byron Moore by Michael Timlin results in a free kick. Steve Phillips restarts play with the free kick.10:30
Centre by Byron Moore, save made by Cameron Belford.8:08
Corner from right by-line taken by Ashley Westwood.7:39
Byron Moore crosses the ball, Mark Phillips makes a clearance.5:02
Corner taken short by Ashley Westwood.4:37
A cross is delivered by Matt Tootle, Ryan Hall makes a clearance.3:12
Inswinging corner taken from the right by-line by Ryan Hall.1:36
Peter Gilbert produces a cross.0:00
The match begins.
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