There were no rules to constrain him, no second time around the order to save himself for. Back in his familiar relief role for the Yankees, this was the same guy who had dominated the American League, firing high-octane fastballs and sliders past a trio of overmatched Blue Jays.
Chamberlain's final line: three strikeouts, no runs, no hits -- no problems.
"It felt great," Chamberlain said. "Just getting going, it's like riding a bike. It didn't take me very long to get going. My arm actually warmed up quicker than I thought it would. Being able to take my time, I tried to make it as realistic as I could."
After preparing Chamberlain as a starting pitcher during Spring Training, the Yankees informed the 22-year-old right-hander on Wednesday that he would begin the season in the bullpen, helping to set up for closer Mariano Rivera.
Chamberlain had gone through some rocky outings over the first few weeks of the spring, bringing a 6.14 ERA into Thursday's game as he had toyed with his developing curveball and changeup.
The three Toronto batters -- Ryan Patterson, Sean Shoffit and Anthony Hatch -- scarcely stood a chance. Chamberlain needed just 11 pitches to dispatch all three, receiving a standing ovation from the Knology Park crowd as he returned to the dugout.
Of the three, only Patterson had played above high Class A ball, spending most of last season at Double-A New Hampshire. Chamberlain said he called Patterson a friend, having played with him in Hawaii during winter ball and also against him a few times in the Minors.
Yankees manager Joe Girardi said the young Jays probably looked forward to the test.
"Maybe they were thinking, 'You know, he started in A-ball last year ... maybe I can get to the big leagues this year,'" Girardi said. "I'm sure they're excited. I'm sure they looked forward to the challenge and I'm sure they looked forward to their at-bats to see what he has."
Watching on television in the Yankees' clubhouse, starting pitcher Ian Kennedy said that Chamberlain hadn't seemed to miss a beat from last year, when he compiled a 0.38 ERA in 19 appearances after joining the club in early August.
"He looks like a different guy when he starts and relieves," Kennedy said. "He just goes after guys. I don't know if he was holding back too much, but he looked like a different guy today.
"He looks, shoot, like he did last year."
Chamberlain said the difference comes in his aggressiveness. His slider is improving, but by being able to rip it loose and not worry about saving anything in the tank for later, his stuff becomes that much more dominant.
"You just attack the zone," Chamberlain said. "You stop worrying about your mechanics and your abilities take over. It was back to the slider that I'm used to throwing, and not babying it."
The Yankees continue to state as part of the company line that Chamberlain will eventually be a starting pitcher, and -- they believe -- a dominant one. Much of that will rely on his ability to develop his secondary pitches, the curveball and changeup, and Chamberlain said that he will use them from time to time this season out of the bullpen depending on situations.
But on days like Thursday, there seems to be little need to delve any deeper into the bag of tricks. He will begin the year in the bullpen, cracking jokes with coach Mike Harkey and sharing setup duties with LaTroy Hawkins and Kyle Farnsworth.
If Thursday's results are any indication, he'll be effective. Just as they did in the second half of last season against much more dangerous competition, the fastball and slider seem to allow Chamberlain to get by just fine.
"If it ain't broke, don't fix it," Chamberlain said. "Don't go away from what got you where you're at. I have to continue to get better at that, but you've also got to continue to expand what you have. Never lose sight of what got you here."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.