|Leicester (8) 22|
|Tries: Crane, Morris Pens: Burns 3, Bell|
|Northampton (9) 14|
|Try: Stephenson Pens: Wilson 3|
Leicester beat a weakened Northampton side already assured of a home Premiership semi-final to secure a play-off away to Bath.
Jordan Crane crashed over in the corner from a line-out, but three James Wilson kicks gave Saints a 9-8 interval lead.
Tigers then dominated up front, leading to a double sin-binning against a scrum unable to repel some intense pressure.
And the boot of Freddie Burns and a Niall Morris try against 13 men secured victory despite Tom Stephenson's try.
Tigers, who are joined in the Premiership play-offs by Saracens, were third prior to kick-off and knew any sort of victory would be enough to prolong their season.
That late Stephenson score inside the final 10 minutes set nerves jangling at a sell-out Welford Road.
|Leicester's play-off pedigree|
|Tigers, 10-time English champions, have not finished outside the top four since 2004.|
But Wilson was unable to add the conversion and Tigers never looked like surrendering an eight-point advantage and a semi-final date in Bath after an impressive second-half display full of power, experience and quality up front.
Northampton's decision to make 13 changes from the side that had already secured top spot and a home play-off semi-final seemingly handed the pre-match initiative to their fierce east Midlands rivals.
Director of rugby Jim Mallinder had also talked of looking at the bigger picture, but there was no evidence of a half-hearted approach from Saints as their second-string stood firm in the face of a bustling Tigers opening.
Burns slotted a simple early penalty and, after England prop Dan Cole was stopped just short of the try line, Crane went over to establish an 8-3 lead following a well-worked line-out.
But Saints were looking sharper at the breakdown and recycling the ball quicker and they began to force Leicester into conceding penalties.
Wilson, who already had one kick to his name, added two more to put the visitors ahead.
However, Leicester's experience up front began to tell after the break and they dominated the forward battle.
The Saints scrum started to buckle and, moments after coming on to replace the struggling Salesi Ma'fu, Gareth Denman was sent to the sin-bin.
Ma'afu returned only to join Denman on the bench after himself getting yellow-carded and Tigers made the most of it, with Morris going over.
Stephenson's try after a fine move gave Saints hope, but Leicester held on to set up an away last-four tie at The Rec.
Leicester Tigers director of rugby Richard Cockerill on the play-off semi-final at Bath:
"It is a one-off game next week, and we are a different side to when we played them down there [Bath won 45-0 earlier in the season at The Rec].
"We have got guys in our side that can win big games. We saw that last week against Wasps, and the pressure is probably not on us. I think we can go there and throw everything at them.
"The crux of it is you have to win next week. We have to win, they have to win, so different pressures come on and people react in different ways.
"We will go there, we will work hard and we will take 6-3 if it comes to it."
Northampton Saints director of rugby Jim Mallinder on the play-off semi-final against Saracens:
"We have had some cracking matches against them.
"The Premiership final was an epic last year [Northampton won 24-20] and we have had some good games this season.
"We know each other quite well, and I think it is going to be a great game."
Leicester: Morris; Goneva, Tait, Loamanu, Thompstone; Burns, Ben Youngs (capt); Mulipola, Tom Youngs, Cole, Thorn, Kitchener, Slater, Salvi, Crane.
Replacements: Replacements: Roberts for Loamanu (71), Bell for Burns (68), Harrison for B. Youngs (67), Ayerza for Mulipola (48), H. Thacker for T. Youngs (67), Balmain for Cole (69), De Chaves for Thorn (58).
Not Used: Gibson.
Northampton Saints: Tuala; Elliott, Waldouck, Stephenson, Collins; Wilson, Dickson; Corbisiero, Haywood, Ma'afu, Dickinson, Craig, Dowson (capt), Harrison, Fisher.
Replacements: Fotuali'i for Elliott (48), Oliver for Wilson (69), Packman for L. Dickson (48), C. Day for Haywood (64).
Not Used: Hartley, A. Waller, Denman, Nutley.
Sin Bin: Ma'afu (53), Denman (53).
Referee: Matt Carley (RFU).