Rachubka was publicly backed by boss Grayson after a mistake handed Coventry a 1-1 draw at Elland Road.
But his shaky form has continued and his manager was in less conciliatory mood on Tuesday, handing 18-year-old Alex Cairns his professional debut at the start of the second half.
Rachubka's problems began in the 13th minute when he could only parry Shelvey's shot into the path of Lua Lua, who knocked in a simple chance.
The keeper then dropped a routine catch, leading to Lees's dismissal for handling Ludovic Sylvestre's goalbound shot - Shelvey's resultant spot-kick was ordered to be retaken for encroachment but the on-loan Liverpool playmaker calmly stroked his second into the bottom corner.
Shelvey's second goal was also a gift as Rachubka dropped a speculative 25-yard Lua Lua shot at his feet as Blackpool opened a 3-0 lead inside the first 30 minutes.
Rachubka was booed as he received a backpass 10 minutes before half-time and Grayson replaced the keeper with Cairns at the interval.
Cairns, who has come through the Leeds academy, kept one Shelvey effort out but could do nothing to stop Lua Lua scoring his second when he cut inside Paul Connelly and fired into the top corner.
And Shelvey made an uncomfortable night for Grayson, against the club he left in acrimonious circumstances in December 2008, even worse when he completed his hat-trick after being played through by Martinez Angel with 12 minutes remaining.
Free kick awarded for a foul by Jonathan Howson on Lomana Tresor LuaLua. Direct free kick taken by Jonjo Shelvey.
Lomana Tresor LuaLua challenges Aidan White unfairly and gives away a free kick. Paul Rachubka takes the direct free kick.
The free kick is delivered right-footed by Robert Snodgrass from right channel, Keith Southern manages to make a clearance.
Booking The referee shows Ian Evatt a yellow card for unsporting behaviour.
Unfair challenge on Ross McCormack by Ian Evatt results in a free kick.
The assistant referee signals for offside against Andrew Keogh. Matthew Gilks restarts play with the free kick.
The offside flag is raised against Robert Snodgrass. Matthew Gilks takes the free kick.
The referee blows for offside. Paul Rachubka restarts play with the free kick.
Tom Lees sends in a cross, save by Matthew Gilks.
Robert Snodgrass delivers the ball, clearance by Alex Baptiste.
12:34 Goal scored
Goal - Lomana Tresor LuaLua - Leeds 0 - 1 Blackpool Lomana Tresor LuaLua grabs a goal from close range to the bottom left corner of the goal. Leeds 0-1 Blackpool.
Jonjo Shelvey takes a shot. Paul Rachubka makes a save.
Unfair challenge on Adam Clayton by Keith Southern results in a free kick. Free kick crossed by Robert Snodgrass, Alex Baptiste manages to make a clearance.
Free kick awarded for a foul by Stephen Crainey on Robert Snodgrass. Free kick crossed left-footed by Robert Snodgrass, Matthew Gilks makes a save. Patrick Kisnorbo takes a shot. Save made by Matthew Gilks.
Alex Baptiste fouled by Adam Clayton, the ref awards a free kick. Matthew Gilks restarts play with the free kick.
Shot by Callum McManaman from just outside the area goes over the net.
Short corner taken by Ludovic Sylvestre from the right by-line.
The assistant referee flags for offside against Andrew Keogh. Matthew Gilks restarts play with the free kick.
The referee gets the game started.
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