World number one Dustin Johnson believes his game is back to its best after he beat fellow American Jordan Spieth in a play-off to win the Northern Trust Open on Sunday.

Spieth had started the final round with a three-shot lead and he raced further in front to lead by five.

However, a double-bogey at the sixth cost him dear as he found the water and then missed a vital putt.

Johnson and Spieth continued to plug away and a sensational putt on the 18th from Johnson forced a play-off.

The duo started on 13-under par on the 18th, but Johnson’s risky drive paid off as he laid down the challenge to his rival.

Spieth missed his putt from distance, while Johnson sunk his with ease and he admits his game is in a good place following the first event of the PGA Tour FedEX play-offs.

“I feel the game’s back in form like it was leading into he Masters,” he told reporters.

“I’m swinging really well, got a lot of control over the golf ball and I’m feeling really good. Getting a win here gives me a lot of confidence going into next week and the rest of the play-offs.”

Both players eventually finished four shots clear of Spain’s Jon Rahm and Venezuela’s Jhonattan Vegas.

England’s Paul Casey could only produce a final-round 71 to finish alone in fifth, while Webb Simpson, Jason Day, Justin Thomas and Kevin Chappell finished in a tie for sixth.