Ken Owens will captain the British and Irish lions
The Wales hooker had entered the tour under the cloud of ankle problem, but has recovered in time to start the second match of a gruelling New Zealand trip.
Ireland's Kiwi-born centre Jared Payne will also start, having recovered from a calf strain that ruled him out of Saturday's 13-7 tour-opening victory over the New Zealand Provincial Barbarians.
Gatland has made good on his promise to field a fully-changed starting XV, with the head coach hailing Scarlets front-rower Owens in fighting back to full fitness.
"In terms of Ken, he has worked really hard on his recovery and it's great to have him available," said Gatland.
"He has captained the Scarlets and has assumed a leadership role within the camp and it is a great opportunity for him.
Ken Owens will captain the Lions against the Blues
Ken Owens has captained the Scarlets and has assumed a leadership role within the camp and it is a great opportunity for him
"We have stated from the off that we want to give every player a start in the first three games and Wednesday is an opportunity for this set of players to show what they can do in a Lions jersey.
"It was good to get the win under our belts last weekend. The boys in the stand were itching to get their chance and they are really excited about Wednesday."
Owens will number among 11 tourists making their Lions debuts in the starting XV to face Tana Umaga's Blues.
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The 30-year-old missed the Scarlets' triumphant Guinness PRO12 play-off campaign after suffering an untimely ankle injury.
But now the gritty hooker has beaten his problem in time to justify the Lions' decision not to replace him in their touring ranks.
British & Irish Lions squad for 2017 New Zealand tour Mon, May 22, 2017
Express Sport runs through the confirmed Lions squad for the 2017 tour to New Zealand
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Express Sport runs through the 37-man Lions squad ahead of the New Zealand tour
Only Leigh Halfpenny, Rhys Webb, Dan Cole and Justin Tipuric boast prior Lions match experience in Gatland's starting line-up.
Dan Biggar has a chance from the off at fly-half, with Johnny Sexton taking a seat on the bench and doubtless desperate to improve on a difficult opening-match performance.
Maro Itoje and Courtney Lawes form an all-England lock pairing, while Payne is joined in the centres by his Ireland team-mate Robbie Henshaw.
British and Irish Lions team to face the Blues on Wednesday: L Halfpenny (Wales), J Nowell (England), J Payne, R Henshaw (both Ireland), E Daly (England), D Biggar, R Webb (both Wales), J McGrath (Ireland), K Owens (Wales, capt), D Cole, M Itoje, C Lawes, J Haskell (all England), J Tipuric (Wales), CJ Stander (Ireland).
Replacements: R Best (Ireland), J Marler, K Sinckler (both England), I Henderson, P O'Mahony (both Ireland), G Laidlaw (Scotland), J Sexton (Ireland), L Williams (Wales).