So he stumbled on the first hole Thursday, hitting a shot long before missing a 6-foot putt to bogey the par-4 No. 1.
"I've been playing every day, but tournament conditions are always different," Watson said. "You get different juices flowing. You get a different kind of rough. No home course can compare to it. But the juices start flowing pretty quickly."
In fact, it took Watson one hole; he birdied No. 2. He later birdied No. 6, but he bogeyed the ninth hole and finished even par through nine.
The leftover rust was completey shaken on the back nine. Watson shot a 5-under 30 and finished at 65, tied for second place at one shot off the leaders.
"The first part is getting used to how fast everything is going, how deep the rough is, and feeling the crowd and feeling all of the energy," Watson said. "Once you get settled, you can get into the flow."
Watson played in the Zurich Classic of New Orleans, Quail Hollow Championship and The Players Championship in three consecutive weeks. But after missing the cut at The Players Championship on May 7 , Watson took three weeks off before the Memorial started June 3.
He tied for 33rd at the Memorial and is now back in Cromwell, where he tied for 14th last year and tied for sixth in 2008. As he ended his round Thursday, Watson was feeling good about the weekend.
"I'm very happy," Watson said. "It's only the first day, and I've still got to play good the next three days. But if I shoot 5-under the next three rounds, I maybe have a chance to be a winner."
Starting off with the bogey, Watson said he was fired up. And after No. 6, he was even more motivated to make up some ground.
And he did on back nine. He found momentum when he birdied the 11th, 12th and 13th holes. On No. 15, he hit a 4-wood on the green and two-putted for another birdie.
His last birdie came on No. 18, where he hit a 9-foot putt.
"Out here, you can make so many birdies," Watson said. "You know, one bogey is not going to slow you down. I got lucky and made some putts and shot a 5-under on the back nine."
Watson is tied with Dustin Johnson for longest driving distance (304.5 yards) on the tour. But Watson said distance is secondary to the short game at the TPC River Highlands, and it was his ability to putt that propelled him on the back nine.
"That's how you know the rust is off," Watson said. "I think it took a little bit to get the juices flowing."