Rory McIlroy says the exploits of rivals Jordan Spieth - named PGA Tour player of the year - and Jason Day have given him "a sense of hunger again".
The Northern Irishman, 26, was deposed as world number one after being sidelined with a broken ankle suffered while playing football with friends.
McIlroy, a four-time major winner, told BBC Sport: "It's motivating to see what these guys are doing.
"You want to work harder, hit more balls, and try to keep getting better."
After finishing a distant fourth behind winner Spieth at the Masters in April and then sharing ninth spot - five adrift of the American - at the US Open, McIlroy missed The Open Championship at St Andrews in July with his injury.
He did not play again until the season's final major, the US PGA Championship in the middle of August, when he was 17th - 11 shots behind Australian winner Day, who finished on a record 20 under par.
"It has definitely given me that sense of hunger again," said McIlroy, referring to the form of Spieth and Day.
|2015 Majors: Spieth||Day||McIlroy|
|Masters: 1st||28th (joint)||4th|
|US Open: 1st||9th (joint)||9th (joint)|
|Open: 4th (joint)||4th (joint)||Did not play|
|US PGA: 2nd||1st||17th|
McIlroy did win both the WGC Match Play event and the Wells Fargo Championship in May, but admitted 2015 was a "lost year".
"I only missed one major, but it was probably the biggest one you could miss," he said.
However, he indicated a similar injury was unlikely to happen again in the near future.
"I, for sure, won't be playing any football in the middle of the season again," said McIlroy.
"I'll still want to play football in the off season and enjoy my time with my friends as that's what we all do, but maybe be a little more careful in the middle of the golf season."