Casey finished joint fifth at last year's Players ChampionshipEngland's Paul Casey will start the final round of the Players Championship one shot off the lead after completing a solid three-under-par 69 on Monday.
Casey, who resumed on the 10th at 08:00 (12:00 GMT), holed a 35-foot birdie putt on the 17th as he improved his score to eight under at TPC Sawgrass.
India's Anirban Lahiri, ranked 322 in the world, leads after carding a 67.
Scotland's Russell Knox and Ireland's Shane Lowry, who aced the par-three 17th on Sunday, are at six under.
Norway's Viktor Hovland hit the second hole-in-one of the third round with a perfect shot on the par-three eighth as he moved to four under.
A total of 25 players are within five shots of the lead as the tournament, which was hugely disrupted by five inches of rain, thunderstorms and strong winds over the first three days, looks set to reach an exciting conclusion.
No English player has ever won the PGA Tour's flagship event, which boasts the richest prize in golf with $3.6m (£2.75m) for the winner from a $20m (£15.31m) prize fund.
But Casey has put himself in an excellent position to challenge for the title. After opening his tournament with a triple bogey, and also dropping a shot on his third hole, the world number 27 played bogey-free golf for the next 44 holes.
"My game plan after making triple on Thursday was actually [to] just play sensible golf and get it in," he said. "It was fairways and greens and try to slowly claw back the shots I gave away so quickly. That plan has not really changed."
The 44-year-old accepted that he has "a great opportunity" to pick up the biggest win of his career.
"I know you guys would say it's not a star-studded leaderboard, it's not the usual suspects, but at every single PGA Tour event, the level of golf is unbelievable."
Casey is joint second with Colombia's Sebastian Munoz and Americans Sam Burns and Doug Ghim.
England's Tommy Fleetwood, who shared the lead after round one, bogeyed the last to drop into the group on five under.
Scotland's Knox has quietly gone about his business this week and crept up the leaderboard with four birdies on his back nine in a bogey-free 68 to sit three off the lead.
He has plenty of support out here this week given he lives a few miles from TPC Sawgrass in Jacksonville and went to the city's university.
The final round is already under way and BBC Sport will have live text coverage from 16:00 BST, with Casey set to tee off at 16:50.
