SAN FRANCISCO – Merkin Valdez is almost two years out from reconstructive right elbow surgery, so the San Francisco Giants aren't about to take a risk with his health now.

The Giants placed the hard-throwing righty reliever on the disabled list Thursday with a strained elbow on his throwing arm, which isn't believed to be related to his surgery on Sept. 27, 2006.

He was slated for an MRI exam Thursday.

Valdez wasn't available for several days late last week because of tightness in his arm, said he was much better, then felt some discomfort again after he made his latest relief appearance Monday night against the Houston Astros.

“We'll find out what's going on,” manager Bruce Bochy said Thursday before the finale of a four-game series with Houston. “We don't want to put him back out there and risk a setback. This guy did have surgery not all that long ago. We want to err on the side of caution and let it clear up.”

When the Giants got Valdez in a trade with the Braves in December 2002 that sent Russ Ortiz to Atlanta, he was considered one of the organization's top prospects. Then the elbow problem derailed what might have been a rapid ascent to the majors.

After missing all of 2007 following surgery, the 26-year-old Dominican made the opening-day roster this season for the first time. Many other clubs expressed interest in acquiring him this spring, too – but Giants general manager Brian Sabean wasn't about to let him get away.

Valdez is 1-0 with a 1.69 ERA in 17 appearances and 16 innings, including one start. He had limited opponents to a .222 average over his last 16 outings with 12 strikeouts and six walks for a 1.20 ERA during that span.

The Giants called up left-hander Alex Hinshaw and purchased his contract from Triple-A Fresno, clearing room on the 40-man roster by transferring infielder Kevin Frandsen to the 60-day disabled list. Frandsen is out of the season recovering from surgery on his ruptured Achilles' tendon.

This will be Hinshaw's first time on a major league roster, and he was expected to be available for Thursday's game after arriving late to the ballpark.

“At this point we need another arm in the bullpen,” Bochy said. “He's been throwing well. He's earned this.”