Facing the Orioles at Fenway Park, Cook will make his first start for Boston this season, replacing Josh Beckett in the starting rotation for one turn.
Cook could have -- and would have -- exercised his May 1 opt-out clause if there was no spot for him on the Major League roster. And while he'll make the one start, what the team does with him after is still unknown.
"Pitching here and contributing in any way is what I want to do, but you know, my main focus is [Saturday]," said Cook. "I got to go out there, take the ball, and after that, we'll worry about that."
Going 3-0 with a 1.89 ERA in four starts for Triple-A Pawtucket, the veteran sinkerballer has allowed the Red Sox to be conservative with Beckett, who has a sore lat muscle.
"This is where I wanted to be the whole time," Cook said. "To actually get the callup and be here and be with the guys I was with in Spring Training and be able to make my first start here, it's unbelievable."
Cook will be up against Jason Hammel, Baltimore's most effective starter so far this season.
Making his first start against the Red Sox this season, Hammel has gone at least five innings and allowed two earned runs or fewer in every game this season.
Hammel took his first loss of the season on Monday against the Yankees, tossing six innings, while giving up two runs on five hits in a 2-1 Baltimore loss.
"He was the reason we had a chance to win that ballgame," Orioles manager Buck Showalter said after the contest. "He's been solid."
Orioles: Reimold placed on DL
The Orioles placed outfielder Nolan Reimold on the 15-day disabled list Friday with a bulging disc in his cervical spine. Catcher Luis Exposito was called up to take Reimold's spot on the roster.
Reimold last played in Monday's game in New York, going hitless to snap a team-high 14-game hit streak. He later alerted the team's athletic trainers that he was experiencing fingertip tingling.
The team's hottest hitter, Reimold is hitting .313 with five home runs and 10 RBIs in 16 games as the O's leadoff man.
Red Sox: Middlebrooks has club's confidence
In his second Major League game, Red Sox top prospect Will Middlebrooks hit second in Friday's loss to the Orioles. He finished the game going 1-for-6 with a double, and he scored his second run in as many games.
Middlebrooks went 2-for-3 with a double, walk and strikeout in his debut Wednesday in a 4-2 loss to the A's.
The ball that rolled between the legs of Boston first baseman Bill Buckner, allowing the Mets to win Game 6 of the 1986 World Series, has been sold at auction for $418,250, The Associated Press reported Friday.
Orioles second baseman Brian Roberts took part in sliding drills and a heavy pregame workout prior to Friday's game against the Red Sox, believing he could be ready for a rehab assignment in the near future.