PCL notes: Vitters bides time for Cubs

While slugging first baseman Anthony Rizzo has earned a promotion, other prospects such as third baseman Josh Vitters are still at Triple-A Iowa, waiting on their chances.

At a quick glance, Vitters' numbers -- .302, 14 home runs, 56 RBIs through Saturday -- would seem to suggest a callup is overdue. That seems especially true with Chicago third baseman Ian Stewart on the disabled list and Luis Valbuena struggling as his replacement.

"They really haven't told me anything specific (to work on)," Vitters said. "I just assume it means I need to get better at everything. I'm not there for a reason. It's because I need to get more repetition, I need to improve every single day as much as I possibly can."

Vitters was the Cubs' first-round Draft pick out of a California high school in 2007 and has progressed slowly but steadily up the Minor League ladder.

The primary criticisms he has endured are his lack of patience at the plate -- his 24 walks this season are a career high -- and his defense (18 errors).

Vitters is not letting himself be too concerned with either number.

"I don't think you can really walk, especially at a high level in the Minor Leagues, unless you're at least feared to some extent by the other teams," Vitters said. "If you get up in the three- or four-hole and you start putting up some numbers, then the walks start coming."

As for his defense, Vitters feels he has improved despite the errors.

"I feel good, I feel really comfortable over there," he said. "I feel a night-and-day difference from playing third base last year. It just comes from constant practice, throwing, kind of studying what I have to do to be the best defender I possibly can be."

Vitters, who is still just 22 years old, said he has become more of a student of the game instead of just relying on his natural skills.

"You definitely learn that you need to take advantage of every edge you can find," he said. "There are some types of resources I haven't used very well until the last year-and-a-half or so. It's really a huge advantage to be able to study the game and learn about yourself."

Vitters said all of the Iowa players realize that with Chicago rebuilding, any of them could have a chance to seize a great opportunity to move up if they perform and work hard.

"We all want to do good here, just like the big leaguers do, because we all want to get up there," he said. "It's a really great opportunity for everyone on this team and I definitely think there will be a couple of guys taking advantage of it."

Long time coming: Memphis right-hander Shelby Miller ended a two-month drought by picking up a victory Friday, his first since May 15. Miller tossed six shutout innings, allowing four hits without a walk while striking out three as the Redbirds beat Oklahoma City, 8-1. The Cardinals' No. 1 prospect had six losses and four no-decisions between his victories.

Exit Sandman: Albuquerque outfielder Jerry Sands became just the second Isotope to hit two walk-off home runs in a season when he blasted a three-run shot to defeat Iowa, 10-7, on Friday night. Sands hit a two-run homer to beat Round Rock, 10-9, on July 5. Robert Stratton was the first Isotope to hit a pair of walk-offs back in the team's inaugural season of 2003.

About Schmidt: The fourth career Triple-A start for Nick Schmidt was his best as the Colorado Springs lefty threw six shutout innings, giving up just one hit and one walk while striking out five, as the Sky Sox beat Tacoma, 3-1, on Saturday. A former first-round pick by the Padres, Schmidt has battled injuries throughout his pro career, but he has been healthy so far in 2012. Schmidt has a career-high 104 innings and is 7-5 with a 3.98 ERA between Colorado Springs and Double-A Tulsa.