Shortly after being recalled from Triple-A by the Orioles in August and beginning a second, if temporary, career as a reliever, the left-hander was in Yankee Stadium, trudging along through his new daily paces. He needed to open a door to a bullpen enclosure, one he hadn't seen in the early stages of his career as one of the Orioles' most prized prospects.
He pulled the door open and was greeted with a shower of sunflower seeds on his head. The booby trap had been put into place with meticulous care by fellow reliever Luis Ayala.
Matusz laughed it off. Some classic bullpen humor is OK, and so, too, is adjusting to a different gig.
"I'd say the biggest change is being ready every day," says Matusz, 25. "As a starter, you throw one day and then get four days off. As a reliever, you've got to be ready every day. You have something to prepare for every day.
"The view isn't as nice from the 'pen as it is from the dugout, but you get used to it."
Matusz, of course, never planned on being a Major League reliever. He was a can't-miss starter in Baltimore's farm system, a hard-throwing left-hander with All-Star potential.
So far, that hasn't materialized the way Matusz or his team had planned, but baseball is a game of reinvention.
Enter Matusz and his new role as a late-inning lefty-specialist stopper. Enter the Orioles as one of the surprise contenders of late September.
How long will it last? Who knows? But Baltimore is in the thick of a pennant race and Matusz has become an indispensable part of it.
"Brian's got a great look about him," Orioles manager Buck Showalter says. "It's like he's found a new toy, got some real positive thoughts going and is real aggressive."
The numbers are proving that out. As a starter, Matusz went 5-10 with a 5.42 ERA in 16 outings. As a reliever, he's compiled a 1.93 ERA in 11 appearances, stranding all nine inherited runners and striking out 13 batters while walking one in 9 1/3 innings.
He's also getting used to the change, to the hours of sitting beyond the outfield wall and waiting to get a phone call while enduring the good-natured ribbing that comes along with membership in a corps of marooned comrades.
For his money, Matusz says he doesn't see much of a difference between opening the game with empty bases and 100 or more pitches ahead of him, and coming in with the bags loaded in a tie game in the eighth.
Pitching is pitching.
"Getting outs, whether it's in the first inning or ninth inning, it's the same," Matusz says. "You still have to get those guys out, get ahead in the count, throw strikes, keep the ball down and let the defense work.
"For me, the only difference between being the starter and reliever is different roles, coming in at different points in the game. But it's still the same game. Getting outs."
The problem was, Matusz wasn't getting enough of them as a starter. This year's struggles got him sent back to Triple-A Norfolk on July 1. He stayed there and made the conversion to relief before being recalled on Aug. 24.
By that time, Matusz had already committed himself to improving his fitness and strength by approaching former big leaguer and current club special assistant Brady Anderson, who oversees player workouts. The two have become friends, and the regimen has paid off for Matusz.
"He had what was a nightmare season for him last year," Anderson said, referring to Matusz's 1-9 record and 10.69 ERA in 12 starts in 2011. "He knew he had to refocus himself, rededicate himself. His [velocity] had slipped last year, but it's back up. He's hit 95 a few times this year.
"He's been really dedicated. As far as his starting stint went, if you look at the numbers, there are some things to not be pleased with, but how he's improved his velocity and improved his frame of mind and dedicated himself to what a pro athlete should be doing with his spare time -- how they should be preparing and continually trying to get better -- is something that's ingrained in him now.
"I don't think he'll ever go back and lose that mentality."
But will Matusz be a starter again? It's hard to speculate at this point, especially during this stirring pennant drive, but given the current state of Baltimore's starting rotation and contract realities, it seems likely that Matusz will once again get a long look as a starter next spring in Sarasota, Fla.
There were some positive signs this year, too.
Matusz had masterful outings against the Yankees and Rays, and, as Anderson describes it, he came within "a pitch or two" of turning losses into victories in a number of 2012 starts.
And this: Prior to being moved to the bullpen, Matusz had held left-handed hitters to a slash line of .223/.281/.384 in 354 plate appearances in the Majors.
"Even when he was not throwing the ball as well as he wanted to as a starter, he was still getting left-handed hitters out," Orioles catcher Matt Wieters says. "He was able to use multiple pitches. And I think that's the one thing [about relieving]. He's able to come in, knowing he's going to pitch one inning, maybe two innings max, and he's going to let all his pitches go.
"It's made his off-speed better, it's made his fastball better, and right now he's in a great role for us and a great role for him, and when he goes back to starting, it should help him be able to put guys away."
For now, the Matusz experiment is working and the Orioles are winning, and Showalter has good reason to be happy about all of it.
"I think it looks like he's enjoying himself," the skipper says. "Ninety percent of it is because he feels like he's making a contribution to our efforts.
"I think it means the world to them to be able to just walk through the locker room ... knowing that they know that they are an important part."