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06/16/11 10:00 PM ET

Injured Blum ramps up rehab workload

PHOENIX -- D-backs infielder Geoff Blum continues to make progress in his recovery from surgery on his right knee.

Blum fielded ground balls for the first time on Wednesday and also took batting practice.

"Things are moving good," Blum said. "I was a little out of rhythm fielding, but as far as strength goes, it was good. A good step forward."

Blum, who was signed to a two-year contract during the offseason, injured his knee early in the spring and underwent surgery just after the season started.

Blum said he expects it will take him another 10 to 12 days before he's ready to go out on a rehab assignment and he would need at least a week's worth of games after that to be ready to be activated.

D-backs have tempting DH option in Wily Mo

PHOENIX -- Wily Mo Pena's numbers with Triple-A Reno are hard to ignore, and with Interleague Play looming, the temptation to promote the slugger might prove too difficult for the D-backs to resist.

Pena is not known for playing good defense in the outfield, but the D-backs are about to embark on a six-game road trip to Kansas City and Detroit, where they will get to use a designated hitter.

It could be a perfect fit for Pena.

The 28-year-old was signed to a Minor League contract during the offseason and has absolutely abused Triple-A pitching. In 59 games, Pena has hit .356 with 21 homers and 62 RBIs. He has reached base at a .431 clip and slugged .739 for an amazing 1.170 OPS (on-base plus slugging).

"It's the way he's doing it," D-backs farm director Mike Bell said. "He's having quality at-bats. Sure he'll swing and miss a few times, but it seems like he's becoming a more mature hitter, a more patient hitter. His walks to strikeouts are reasonable [23 to 45]. The most impressive thing is the kind of person he is. I heard that he was, but I was completely blown away by what he's done for the clubhouse environment there and the young kids."

After the six-game road trip, the D-backs play three games at home, where the DH would not be used, before heading to Oakland for three more with a DH.

Pena has turned it up a notch the last 10 games, hitting .395 with a .452 on-base percentage and an .895 slugging percentage.

Pena has played a little first base to go with left field, but his best position is with the bat in his hands.

"You're getting Wily Mo, you're getting a big bat and a presence in the lineup," Bell said. "He works hard at [defense]."

Gibson mindful of Hernandez's workload

PHOENIX -- D-backs manager Kirk Gibson has tried to be cautious with how he has used setup man David Hernandez.

Despite that, though, the right-hander had appeared in 33 games heading into Thursday's series finale with the Giants and is on pace to appear in nearly 80 games this year.

The 26-year-old was a starter during his time in the Baltimore farm system before shifting to the bullpen last year. He appeared in 41 games for the Orioles last season, eight as a starter. The D-backs dealt third baseman Mark Reynolds to Baltimore for Hernandez and Kam Mickolio during the offseason, and Hernandez has proven to be one of the team's most reliable relievers.

"You worry about him because he's really been a starter," Gibson said. "So we've held him out, we've given him days off, but we're in uncharted territory."

Hernandez is 2-2 with a 2.81 ERA as the team's primary setup man. He also saved two games when closer J.J. Putz was unavailable. With the D-backs playing so many one-run games and in the thick of the National League West race, the temptation to use Hernandez is great.

"We haven't extended him unreasonably," Gibson said. "I think I probably could have pitched him more, but have not thinking of the long range. It's my belief that if I continued to do that [extend him], he wouldn't be healthy for us all year. So you have to balance that."

Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @dbackswriter. This story was not subject to the approval of Major League Baseball or its clubs.