ARLINGTON -- Before Spring Training started, all Justin Grimm wanted to do was earn a spot on the Rangers' Double-A team.

He has far exceeded those expectations. Not only was Grimm promoted to Frisco before his second season since being drafted by the Rangers in the fifth round in 2010, but he will make his Major League debut when he starts for the Rangers on Saturday against the Astros.

"At the start of the season, I didn't see myself possibly pitching in the big leagues this year," Grimm said. "My goal, personally, going into Spring Training, I just wanted to show them that I continued the process through the offseason in my work in hopes to make the Frisco team. That's what I looked forward to."

Grimm will fill a gap in the Rangers' rotation left open by Alexi Ogando, who suffered a strained right groin in his first start of the season Sunday against the Giants. Ogando, taking over for an injured Derek Holland, had thrown three scoreless innings before hurting himself running to first base. Now it's Grimm's turn.

"It was very overwhelming. It was kind of unexpected, to be honest," Grimm said. "When [manager] Ron [Washington] took me into his office, he told me, 'It's the same pitches in Double-A and here. If you make them, you're going to have success. If you don't, they're going to hit mistakes.' I feel like if I can make my pitches, I'll be all right."

Before speaking with Washington, Grimm was informed that he was getting called up by his manager in Frisco, Steve Buechele. As soon as he arrived at the ballpark, Buechele called Grimm into his office. After telling Grimm that he had been named a Texas League All-Star, Buechele relayed some more good news.

"He said, 'Have your parents left yet?' I said, 'No. I'm waiting to say goodbye,'" Grimm recalled. "He goes, 'Good. While you're at it, you can get them a ticket to Arlington's game tonight. Because you're going to pitch Saturday.'

"My jaw kind of dropped, my heart started beating fast, and my knees started shaking. But that's good. I want that feeling. It's a feeling I'm never going to forget."

In 14 appearances, 13 of them starts, with the RoughRiders this season, Grimm, a University of Geogria product, has posted a 8-3 record and a Texas League-leading 1.87 ERA. His eight wins are second in the league behind only teammate Barrett Loux (11-0).

"I wouldn't say I was a pitcher coming out of college, I was more of a thrower," Grimm said. "Once I got to professional baseball, I just kind of showed up with the attitude of, 'What could I learn today?' I think that's played a big part in how I've come so far in such a short time."

Grimm has struck out 67 and walked only 14 this year, while holding opposing hitters to a .228 batting average. He has turned in quality starts in each of his last four outings, which included a streak of 25 consecutive scoreless innings.

"In my opinion, I'm a power pitcher," Grimm said. "I've got a good fastball. It's my go-to pitch. I've been able to command it really well lately. I have a slurve. I'm still continuing to develop a changeup, but it comes sometimes and goes. Hopefully Saturday, it's something that I have. I'm definitely going to need it."

Grimm said his mother, father and sister will be in attendance at Rangers Ballpark in Arlington on Saturday. His brother will be unable to join them as he is serving as the best man in a wedding.

"You should feel yourself having the potential to pitch in the big leagues one day," Grimm said. "Why show up every day if you don't feel that way?"