CHALLENGE CUP Semi-final, Second Leg: Sunday, April 24Sale Sharks (25) v Connacht (18), Edgeley Park, 1.00pm (live Sky Sports 2)
Lacey's shoulder has failed to recover sufficiently and he is a notable absentee from the 26-man squad that coach Michael Bradley named on Thursday morning.
The 27-year-old Lacey has been in excellent form for Connacht of late, scoring four tries in his last five Celtic League outings, and twice in the province's last two European ties.
The westerners are still waiting on four forwards and two backs to prove their fitness ahead of the Stockport showdown, with Peter Bracken (back), Ray Hogan (hamstring), Dan McFarland (shoulder), John Fogarty (neck), Darren Yapp (hamstring) and James Downey (calf) all trying to shake off knocks.
Bradley has included Corinthians and Ireland Under-21 forward Joseph Merrigan - one of the westerners' three additions for the Cup's knock-out stages - as hooker cover.
Meanwhile, Connacht second row and skipper Andrew Farley - who scored the first leg's opening try at the Sportsground three weeks ago - is still hoping to end a topsy-turvy season with European glory and an historic place in next season's Heineken Cup.
The Australian - who has started all 27 of the westerners' competitive games this season - admitted: "We are all focused on securing the victory that is require this weekend. We are looking to earn our right to compete in a European final and we will leave no stone unturned in attempting to achieve this."
Connacht's last visit across to the Sharks' Edgeley Park four seasons ago coincided in a 44-6 loss, but coach Bradley is in determined mood to end his side's current poor run of form.
Connacht have lost four times in the last month, yet still have the armoury to counter Philippe Saint-Andre's men, who boast four British and Irish Lions squad members.
"We are fully aware of the threat they pose, in particular at scrum time and on counter attacks. We will be looking to do some work to combat these areas in the coming days," insisted the former Ireland scrum-half and captain.
"We can do it and qualify for the final - if we play well.
"However we do have to close down their exceptional back three of Jason Robinson, Steve Hanley and Mark Cueto and keep a close handle on them while matching their power up front.
"We expected everything they threw at us in the first leg and there were no surprises. The second leg should be very similar," added Bradley.
The Sale side, announced on Friday, includes England fly-half Charlie Hodgson - who missed the first leg - as well as former Scotland scrum-half Bryan Redpath - who came on to good effect in Galway. Tighthead prop Ben Coutts will make his first start for the Sharks since joining from Ebbw Vale.
The prize for the semi-final winner is a Saturday, May 21 date against either Pau or Brive at Oxford's 12,400-capacity Kassam Stadium.
Both the 2004/05 Challenge Cup final (kick-off 12.45pm) and European Shield decider (5.00pm) will be held in Oxford on May 21, and televised live on Sky Sports.
2004/05 Form: Sale: W33-21 v Catania (away), W50-3 v Catania (home), W33-15 v Narbonne (away), W25-10 v Narbonne (home), W34-18 v SU Agen (home), L15-17 v SU Agen (away), W25-18 v Connacht (away)
Connacht: L11-25 v Narbonne (away), W40-21 v Narbonne (home), W56-3 v Montpellier (home), L14-19 v Montpellier (away), W26-21 v Grenoble (away), W19-3 v Grenoble (home), L18-25 v Sale (home)
Top Scorers: Sale: Mike Hercus, Charlie Hodgson both 51 points; Mark Cueto 5 tries; Connacht: Paul Warwick 91 points; Warwick 4 tries
Previous Meetings: Sale 2, Connacht 0(2001/02: Connacht 30 Sale 33; Sale 44 Connacht 6)
Best Finishes: Sale: Winners, 2001/02Connacht: Semi-finalists, 2003/04
Sale: Jason Robinson (Capt); Mark Cueto, Jos Baxendell, Robert Todd, Steve Hanley; Charlie Hodgson, Bryan Redpath; Andrew Sheridan, Andy Titterrell, Ben Coutts, Dean Schofield, Fernandez Lobbe, Jason White, Chris Jones, Sebastien Chabal.
Replacements (from): Sebastien Bruno, Stuart Turner, Barry Stewart, Peter Anglesea, Magnus Lund, John Carter, Chris Rhys Jones, Mike Hercus, Sililo Martens, Richard Wigglesworth and John Payne.
Forwards: Ray Hogan, Dan McFarland, John Fogarty, Joseph Merrigan, Bernard Jackman, Stephen Knoop, Adrian Clarke, Tony Buckley, Christian Short, Andrew Farley (Capt), Paul Neville, Michael Swift, Brendan O'Connor, John O'Sullivan, Michael Carroll.
Backs: Mike Walls, Chris Keane, Eric Elwood, Paul Warwick, James Downey, Mark McHugh, Darren Yapp, Conor McPhillips, Ted Robinson, David Slemen, Matt Mostyn.
Referee: Rob Dickson (Scotland)