MEMPHIS, Tenn. -- While shortstop Paul DeJong continues his run of success with the Cardinals, Aledmys Diaz remains down in Triple-A Memphis, where he's working to prove that he's ready to return to St. Louis and compete with DeJong for starting opportunities.

Diaz was caught off guard by the Cardinals' decision to send him to the Minors on June 28. At the time he was slashing .260/.293/.396, struggling with pitch selection and dealing with nagging injuries to his thumb and ankle. He was also leading the Cardinals in hits, with 71.

"I took it as a surprise when they sent me here, but at the same time, you can't control that," Diaz said. "I don't understand why they [made that decision], but I'm a professional, so I came here and [I'm] working. I'm feeling better. I know I can be a better player."

While in Memphis, Diaz has been working with hitting coach Mark Budaska, who spent a few weeks on the big league coaching staff last month while Bill Mueller was dealing with a personal matter. Budaska, in his 10th season as the Redbirds' hitting coach, also worked with Randal Grichuk after he was demoted in late May.

One focus of their work is helping Diaz improve his plate discipline and pitch recognition. According to Statcast™, Diaz swung and missed at 14 percent of the pitches outside the strike zone this season in St. Louis, 5 percent higher than last year.

"Seeing the ball is probably one of the biggest things, managing the strike zone properly and not getting yourself out," Budaska said. "He was playing not at 100 percent, and it's hard to hit when you have sore hands and feet for your balance and quickness.

"I don't think we'll have any problems working with each other and getting the plan and achievement where he wants to get back to."

So far the results have been slow in coming. In 11 games, Diaz has hit .217/.229/.348, and he endured a 1-for-18 stretch before posting multihit games in two of his last three appearances.

Though Diaz had to step away after Saturday's game to deal with a personal matter and has not played since, general manager Michael Girsch said he is expected to rejoin Memphis on Friday.

"I think for me it's about being comfortable at the plate and swinging at pitches in the strike zone and being more aggressive with the pitches and at the same time being patient and taking more pitches," Diaz said. "I think this is a tough game, and it's about having confidence in yourself."

The second-year shortstop is hoping to regain his confidence and rediscover the success that made him an All-Star last season, when he slugged .510 and drove in 65 runs. This year he reached the midway point of the season with 20 RBIs

While he works, he also continues to pay attention to what's happening in St. Louis. He watches as many games as he can, hoping for the opportunity to return.

"They have a plan for me. They have a process. You have to trust in that process," he said. "I came here, and I have to be a professional. Sometimes you get frustrated, because you don't agree with these things, but at the same time, you have to get here and work harder."

Alaina Getzenberg is a reporter for MLB.com.