PHOENIX -- When D-backs manager Kirk Gibson talks about the importance of defensive positioning and having his pitchers in sync with their fielders, it can be a little hard for some to understand fully.

On Sunday, Gibson used an example from the previous night's game to illustrate his point.

In the decisive seventh inning, Freddy Sanchez broke the game open with a grounder through the hole at short off Sam Demel. The ball was not hit hard -- and a few feet either way it would not have been a problem -- so the assumption was that it was a good pitch that had a bad result.

"He gave up a ground ball. But the reality of it is, he missed his spot," Gibson said. "It was a sinker -- supposed to be down and away -- and it ran right over the middle, inner third. It's important that he hit that spot because of the way we are defending that hitter. We've not done a good job at that. For me, I have to make sure they understand what we're trying to accomplish. I can't assume that."

In other words, the D-backs were not playing Sanchez to pull because they were planning on pitching him away -- so when the pitch was inside instead, Sanchez was able to pull the ball for a hit.

Gibson made it clear he was not singling Demel out and that he did not mean his explanation to be "derogatory towards Sam." He was simply pointing out what has been a staff-wide problem.

"Our pitching has to improve," Gibson said. "We haven't made pitches. The pitching side we're well below average, and that's where our success lies."

Montero has been team's iron man

PHOENIX -- Miguel Montero has been the iron man so far this season.

The D-backs catcher has started 13 of his team's first 14 games, including Sunday's day game after a night game with a left-handed pitcher on the mound.

"We've had a lot of off-days, and he's obviously a big part of our team -- swinging the bat well, getting a lot of production," Arizona manager Kirk Gibson said of Montero. "He feels good."

Montero has been one of the D-backs' best hitters, entering Sunday's game with a team-best .415 batting average to go along with a .707 slugging mark and a .500 on-base percentage.

Veteran backup catcher Henry Blanco has made just one start and has four at-bats. Isn't it hard for him to stay sharp?

"I don't think so," Gibson said. "He catches bullpens, he's been out throwing early, he's a veteran guy. I think he's fine."

Blanco should get more time in the coming weeks, as the off-days become scarcer. The D-backs start a stretch of 13 games in 13 days starting on Tuesday.

"So I'll have to give him some days off in that streak," Gibson said of Montero. "I just thought with all the off-days, I was going to play him."

Blum, Duke making progress

PHOENIX -- Third baseman Geoff Blum has begun working out in the D-backs' extended spring program at Salt River Fields.

Blum has been out of action since early March, when his right knee began to swell up on him. Tests revealed that the veteran is missing some cartilage in the knee, and he received injections of a synthetic gel to try and alleviate the problem.

If all goes well, Blum could start out on a rehab assignment at the end of this week, according to D-backs manager Kirk Gibson.

Meanwhile, pitcher Zach Duke is continuing to play long toss to rebuild arm strength, after being sidelined since early March with a pair of fractures in his pitching hand.

The left-hander is up to playing catch from 120 feet. After another week or so of that, he could be ready to start throwing bullpen sessions.