Summerhays and Thompson started the day tied for the lead, two shots ahead the pack.
But Thompson fell out of contention quickly with a double bogey on No. 5 and a bogey on No. 8. He finished fourth at 18 under, two shots back after a 71. Summerhays moved into the lead with a birdie on No. 9, but made bogey on 14 and fell behind until making birdies on both Nos. 17 and 18.
It was the second straight week Summerhays failed to close a tournament after having at least a share of the lead on the final day. His drive on the playoff hole the 5,532-yard, par-5 18th found the bunker on the right side of the fairway and he hit into the water on his second shot.
He tied for fourth the week before at the John Deere, a stroke out of a playoff after bogeying the final hole.
Austin wasn't the only veteran making a move on the final day.
Beckman, a 43-year-old, recovered from a 72 in the opening round to post a 64, 65 and 67 in the final three rounds. He was tied for the lead at various times Sunday. He drilled an impressive 15-foot birdie putt to force the playoff, but his 5-foot putt on the playoff hole missed to the right.
Billy Andrade charged up the leaderboard with a 65 to tie for fifth at 17 under. The 49-year-old started the day seven shots off the lead but climbed quickly by shooting 7 under through his first 11 holes. He finished with seven straight pars.
It was the first day of the tournament that didn't involve a weather delay. But there was plenty of heat and humidity as well as some wind for the first time all week as players dealt with a soft course that received more than an inch of rain overnight.
____
Follow David Brandt on Twitter: www.twitter.com/davidbrandtAP