And then Jason Day made him do a little bit more.
Walker was standing over an 8-foot birdie putt on the par-5 17th hole Sunday when he heard a roar that caused him to twice back off the putt. It was Day, the defending champion and world's No. 1 player, down to his last chance and delivering with a 2-iron that landed in front of the pin and stopped 15 feet away for eagle.
Walker answered, like he had done all day, with a birdie for a three-shot lead.
Moments later, another roar.
Day made the eagle putt, and the lead was down to one.
"There was nothing easy about the day -- really about the week, for that matter," Walker said. "Especially coming down the last hole."
He went for the 18th green knowing it was his easiest chance for the par he needed to win. The outcome was still in doubt until Walker missed the green to the right, pitched out of deep rough to 35 feet and rolled his first putt about 3 feet past the cup.
Walker calmly made it to capture the PGA Championship, ending a long and wet week at Baltusrol, and still having just enough strength left to hoist the 37-pound Wanamaker Trophy.
"He really put it on me to make a par," Walker said. "Sometimes pars are hard. But we got it."
That par gave him a 3-under 67 and a one-shot victory and made the 37-year-old from Texas a major champion. Even with the silver trophy at his side, Walker still had a hard time letting that sink in.
Because of rain, the 36-hole final was the longest in PGA Championship history since Jim Turnesa won his 36-hole match in 1952. Walker at least had time to rest in his travel bus -- he's a frequent neighbor of Day on the PGA Tour -- and get right back out into the final round. Walker, who shot a 68 in the morning for a one-shot lead over Day, didn't make a bogey over the last 28 holes.
Day, trying to join Tiger Woods as the only back-to-back winners of the PGA Championship in stroke play, came out to the 18th green with his son to watch the finish and quickly found Walker. "Great stuff, mate," he said.
"It was nice to get the eagle, just to try and make Jimmy think about it," Day said after a 67. "But obviously, Jimmy just played too good all day."
In a most peculiar final day at a major, the PGA Championship allowed for preferred lies -- that never happens in a major -- because of nearly 4 inches of rain during the week that drenched the Lower Course. Desperate to beat the clock and avoid a second straight Monday finish at Baltusrol, the pairings stayed the same for the final round.
Walker and Day were playing with occasional mud on their golf balls on the back nine of the third round Sunday morning as some players behind them were able to lift, clean and place their golf balls in short grass in the fourth round.
But it ended on a happy note for Walker. He is a major champion, completing a sweep of first-time winners in the majors this year. Better yet: It moved him from No. 29 to No. 4 in the Ryder Cup standings, all but assuring him a spot on the team.
He finished at 14-under 266, one shot from David Toms' record score in the 2001 PGA Championship.
Walker began the back nine by holing a 45-foot bunker shot on No. 10 and making a 30-foot birdie putt on No. 11. The final birdie on the 17th was the most important because he had a cushion. And thanks to Day, he needed it.
"Two-putting from that is pretty difficult, especially trying to go for your first major," Day said. "But he's handled himself pretty good."
British Open champion Henrik Stenson, trying to join Ben Hogan as the only players to win back-to-back majors at age 40, faded with a double-bogey on the 15th hole.
"It was a long day. I never felt like I brought my 'A' game," said Stenson, who started the final round two shots behind and closed with a 71. "I think I hit more poor shots in the two rounds today than in the previous six or seven rounds combined."
For the second straight major, this became a duel over the final hour.
Day pulled within one shot with a 20-foot birdie putt at No. 11, but he never had another birdie chance closer than 25 feet until the two par 5s at the end. Even so, the Australian battled to the end with the second of two 2-irons at 18 leading him to shout, "Get back there!" And it did.
Thanks to Walker holding his nerves, it just wasn't enough.
"God, just to be in it and be there and have a chance and then to finish it off is just ... it's so gratifying," Walker said.