Graeme McDowell and Russell Knox head into a Monday finish at the OHL Classic at Mayakoba in a share of the final-round lead.
Rain led to a delay at the El Camaleon Golf Club before darkness suspended play with McDowell and Knox leading at 19 under.
McDowell was six under through 13 holes and Knox had picked up six shots through 12 to be two strokes clear atop the leaderboard.
Jason Bohn remains in contention in outright third, two shots ahead of Scott Brown and overnight leader Derek Fathauer.
McDowell is searching for his first PGA Tour win since 2013 and he was blemish-free on Sunday.
The Northern Irishman holed a hat-trick of birdies starting at the fifth before three in four holes on the back nine.
Knox made a flying start to his round as the Scot, fresh from his win at the WGC-HSBC Champions, produced five birdies on the front nine.
He picked up another shot on the back nine and is well-placed heading into the extra day's play.
Bohn and Fathauer are through 12 holes, while Brown is four under after playing 14 final-round holes.
Seemingly too far back to win are a group of four players at 13 under.
Patrick Rodgers (through 15), Freddie Jacobson (13), Justin Leonard (13) and Harold Varner III (13) will need some luck to claim an unlikely title.
The only player in the top 10 to have completed their round is Keegan Bradley, who carded a five-under 66.
The American is joined by Zac Blair, Spencer Levin, Brice Garnett and Johnson Wagner at 12 under.