MIAMI • Golf's world No. 1 Jordan Spieth was unable to finish strongly at the PGA Tour's Valspar Championship as he had hoped, posting a final round two-over 73 to finish at even-par 284 and a share of 18th place.

The American appeared to have mastered the Innisbrook resort's Copperhead Course over the previous two days, going seven under for those two rounds, but he could not maintain that momentum.

The reigning US Open and Masters champion took a bogey at the second, birdied the par-five fifth, but made double-bogey at the par-three eighth and a bogey at No. 11 to doom his title bid.

The tournament was won by South African Charl Schwartzel, who parred the first play-off hole to defeat American Bill Haas. Both had finished 72 holes on 277.

Schwartzel came from five shots behind in the final round to card a 67 before beating Haas (72) with a tap-in par at the first extra hole.

Spieth's frustration with his inability to figure out green speeds was evident in his post-round comments.

"I couldn't trust any of my putts to get there," said the 22-year-old.

"There's just no way when you get up there to think I actually have to hit it that hard and that high and so at some point, you know, it's just not going to happen. That's rare."

He will now take some time off, skipping the Arnold Palmer Invitational at Bay Hill next week, to prepare for his title defence at next month's Masters.

The biggest thing Spieth said he wants to work on is decision-making, along with his caddie Michael Greller, which he felt derailed his final round on Sunday.

"Really poor from both me and Michael today," said the player.

"Our decisions cost us a few shots early and the momentum."

Spieth said he is close to the level he needs to be to retain his Masters title. "Ball-striking is getting close," he said. "Everything is, I would say, in a good place as far as being ready for the Masters."

AGENCE FRANCE-PRESSE, REUTERS