A subsequent roster move has yet to be announced.
The Jays recalled lefty Marc Rzepczynski from Triple-A Las Vegas to fill Marcum's spot in the rotation for now.
Marcum will undergo an MRI exam likely on Sunday or Monday to make sure there is no hidden damage, but Anthopoulos was confident that the results would come back clean. With the All-Star break near, the Blue Jays are optimistic that Marcum will only miss one start and be ready to rejoin the rotation soon.
Anthopoulos emphasized that the move was more precautionary than anything else.
"We've been more proactive then we ever have before," Anthopoulos said. "If a guy's a little sore, especially coming off Tommy John -- a lot of guys want to fight through it and battle through it -- we're not going to take any chances. The All-Star break is coming up. It's one start.
"We're very, very confident that he's going to be fine. We fully expect him to be in that rotation right after the break."
Marcum, who missed all of last season, has gone 7-4 with a 3.44 ERA through 17 starts this year for the Jays. The 28-year-old ranked seventh in the American League in innings (107 1/3), putting him on pace to easily surpass the career-high 159 frames he logged for the Jays in '07.
The Blue Jays have been careful with Marcum's pitch count up to this point, and the club wants to closely monitor his workload as the season wears on. The stint on the disabled list could help provide Marcum with a midseason breather -- similar to what he required at one point during his rehab last year.
"Shaun would be the first guy to tell you that he's fine," said Anthopoulos, who met with Marcum, manager Cito Gaston and head trainer George Poulis on Friday morning. "He said he went through this last year -- where he stopped throwing for a week, and then he was right back at it and he was fine.
"Like I told Shaun, and I told him this in Spring Training, too, I said, 'Look, we're going to be overly cautious with you. You know how important you are and you know how good you are."
On Thursday, Marcum picked up a loss on the road against Cleveland after allowing six runs (five earned) in just four innings. The righty had an uncharacteristic three walks and two wild pitches in the 79-pitch effort. Gaston said Marcum did not complain about any soreness during the outing.
Marcum opened this season with a 5-1 record and a 2.59 ERA, pitching into the seventh inning in eight of his first nine starts. The right-hander also boasted a 7-1 mark in starts that followed a team loss prior to Thursday. Since throwing a season-high 112 pitches on June 2, Marcum has posted a 5.54 ERA and exited in five innings or fewer in three of five outings.
Like Anthopoulos, Gaston made it clear that the Jays believe Marcum's injury is not considered serious.
"It's minor, so far. We'll see," Gaston said. "He shouldn't miss that long. He kind of came to us and just told us it was a little sore. We just want to be cautious about it. We want him to finish the season out and, by skipping a turn or two there, then it might give him that chance to come back after the All-Star break."