BOSTON -- The Boston Red Sox elected to send Daniel Bard to Triple-A Pawtucket to work out his pitching issues, manager Bobby Valentine said Tuesday.

The decision was made in the aftermath of Bard's last start Sunday in Toronto, in which he walked six and hit two batters in 1 2/3 innings.

The Red Sox activated outfielder Darnell McDonald to take Bard's roster spot.

Bard will continue to work as a starter in Pawtucket, at least for the time being, Valentine said. Daisuke Matsuzaka is pitching Tuesday night in Pawtucket and will be limited to three innings; a decision on whether he will take Bard's spot in the rotation Saturday will be made after that, the manager said.

"Ben (Cherington) and I met yesterday and we met with the coaches today," Valentine said. "We felt it was the best thing for the organization and Daniel to work on his mechanics and not have to worry about his big league record and teammates. He thinks it will be a quick turnaround."

The pitcher was opposed to the demotion, Valentine said. "He thought he could find it on the fly. But we're taking a conservative route."

Bard, who turns 27 on June 25, never has been back to the minors since making his major league debut on May 13, 2009. His conversion from shutdown setup man to starter has been rocky. In 10 starts and one relief appearance, he has a 5-6 record with a 5.24 ERA, and has walked 37 batters in 55 innings.

After his outing in Toronto, Bard talked about the difficulties he has encountered in making the transition.