The Orioles' most heralded pitching prospect is coming up to start Sunday, but at the expense of one the club's other top young hurlers.

The Orioles announced after their 4-1 Opening Night victory against the Tampa Bay Rays that left-hander Brian Matusz will be placed on the disabled list with an intercostals strain near the left side of his back. He will be sidelined roughly a month.

"Could be anywhere from three to five [weeks] to four to six weeks," Orioles president of baseball operations Andy MacPhail said. "You've just got to play it out."

To make room for Matusz, the Orioles are calling up 23-year-old lefty Zach Britton, who allowed just three runs in 20 innings this spring but was sent down Monday to get more time at Triple-A Norfolk and to delay the start of his service-time clock.

Britton learned the news from MacPhail just before 10 p.m. Friday.

"Shocked, I guess that's the only way to say it," Britton said.

Britton will make his major league debut Sunday against Rays' right-hander Wade Davis. Chris Tillman, who was supposed to pitch Sunday, will instead start Saturday night against James Shields.

"In my view, Chris' day is [Saturday], he can pitch [Saturday]," MacPhail said. "Zach is eligible to pitch on Sunday, and we can sort of keep things in line."