Rory McIlroy has carded a second-round 65 at the World Golf Championship event in Mexico to storm ahead at the midway point of the competition.
McIlroy, whose only other appearance this year came at the South African Open in January, carded six birdies and one eagle during Friday's session at Chapultepec Golf Club.
There was to be a blemish on the Northern Irishman's scorecard on the 12th and 17th holes, however, as he dropped shots on both to ensure that things remain tight heading into round three.
Mickelson and Fisher both carded rounds of 68 to find themselves seven-below par overall, while Thomas's 66 - despite three bogeys - leaves him in a chasing pack of three just off the leader.
Dustin Johnson is in a share of fifth place alongside Andy Sullivan and Daniel Berger, meanwhile, and overnight leader Lee Westwood is down in 15th after failing to build on an impressive opening-round showing.