Jackson settling in as a reliever

Jackson settling in as a reliever

CHICAGO -- The Cubs' Edwin Jackson seems to be making the transition from starter to reliever. The right-hander has not given up an earned run over nine innings in his last six outings, and held opponents to a .171 average.

"I always thought he could [pitch in relief], even back in the day in Tampa," Cubs manager Joe Maddon said Sunday of the right-hander, who was on the Rays staff in 2007-08. "His stuff was really good [Saturday]. He was very assertive with all his pitches and his breaking ball was really good. Hopefully, that's a sign of things to come with him."

• How long will it take Maddon to feel he has a good enough sample size to know whether having the pitcher bat eighth is more effective than ninth? The Cubs manager said it may take the entire season.

"I like the idea of being able to [pinch]-hit a little sooner," Maddon said. "If you've got a guy pitching deeply in a game, and you get caught in a situation with bases loaded and two outs, then you have to make a decision. But that could happen anywhere in the batting order."

Justin Grimm, who has been on the disabled list since April 2 with inflammation in his right forearm, was to join Triple-A Iowa for a rehab assignment on Sunday. Grimm was on the Cubs' Opening Day roster but never appeared in a game before going on the DL. He has been rehabbing at the Cubs complex in Mesa, Ariz.

• The Cubs claimed right-handed pitcher Anthony Varvaro off waivers from the Red Sox, and lefty Joseph Ortiz was designated for assignment to make room on the 40-man roster.

Varvaro, 30, was 7-9 with 20 holds, one save and a 3.23 ERA in 166 Major League relief appearances with the Mariners, Braves and Red Sox. He's held left-handed hitters to a .201 batting average in his career.

In nine relief appearances this season for the Red Sox, he gave up five earned runs over 11 innings. He was designated for assignment on April 29.

Ortiz, 24, was 0-1 with one save and a 3.38 ERA in eight relief appearances with Triple-A Iowa this season.

Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.