Confidence is key for record-breaker Roger Federer

(CNN) -- You can't imagine that one of the greatest players in tennis history has ever lacked confidence, but Roger Federer is bubbling with it again after bouncing back from some heartbreaking defeats in the past few months.

The former world No. 1's record-breaking fourth title at the Indian Wells Masters event in California on Sunday extended his winning run to 15 matches -- and 37 from 39 since Novak Djokovic saved match-point to win their epic U.S. Open semifinal in five sets last September.

Federer won the end-of-season ATP World Tour Finals in London, but his bid for a first grand slam title since 2008 ended in the semifinals of January's Australian Open as he lost to longtime rival Rafael Nadal.

He reversed that defeat in the last four on Saturday and now has a 10-18 record against the Spaniard, but denied it was a revenge victory.

"I'm just happy that my run has been so successful and so good," the 30-year-old, who also equaled Nadal's record of 19 Masters 1000 titles, told CNN after beating American John Isner in the final.

"I had a tough loss at the U.S. Open ... it was important that I showed a good reaction. I've on an incredible run now. I've won six of my last eight tournaments and I'm feeling really good and very happy to play. Being on this run and getting some confidence is great."

The 16-time grand slam champion has now collected three consecutive ATP Tour titles, becoming the first man to win four times at Indian Wells -- six years after his last triumph at the U.S. hard-court event.

"I'm confident. Mentally I'm really fresh, despite playing a ton already this year ... I just think overall my game is very good at the moment and I hope I can take advantage of that," he said following his 7-6 (9-7) 6-3 win over the big-serving Isner, who has cracked the top-10 rankings for the first time.

Isner, 10th in this week's ATP listings, reached the final after eliminating world No. 1 Djokovic on Saturday.

"I thought John had a terrific tournament," said Federer. "Now he's installed himself in the top 10, I think he'll stay there for quite some time because he's a player with probably the best serve in the game right now."

Federer said the 26-year-old also makes the most of the height advantage he has over most opponents.

"I think his serve is overall more sound," he said. "He knows when to use which serve. He's volleying well and he's got a great forehand.

"I think he uses his size well and that's why I'm sure he's going to be around for a long time."

Both Federer and Isner will be in action at the Miami Masters, which starts on Wednesday.