"Let me throw more before the game," Perez said. "If I throw more, I have more feeling with the ball."

Perez upped his pregame pitch count from 30 or 35 to 50 on Friday night, working one at a time on his fastballs, breaking ball and changeup. Then the Rangers' No. 2 prospect threw 101 pitches that counted.

And it was clear that a change in his preparation off to the side -- he also lengthened his long-toss routine -- led to success on the main mound. Perez allowed one hit over seven innings in the Express' 2-0 win over the visiting Oklahoma City RedHawks.

Perez (4-5), who surrendered nine runs over his previous two outings, struck out five, walked five and gave up only Brandon Barnes' leadoff double in the third. He retired his final 11 batters.

"After the hit, [I told myself], 'OK, let me get a ground ball, let me throw a quality strike,'" Perez recalled thinking.

The 21-year-old left-hander's ERA dropped below 5.00 -- to 4.90 -- for the first time since May 7. That also was the time Perez earned a win, limiting Memphis to a run on four hits over seven frames.

Perez termed Friday's performance his second-best start of the season, despite the five free passes he issued.

"I don't think about my walks," said Perez, who sports an unseemly 45-to-36 strikeout-to-walk ratio over 75 1/3 innings. "I see a lot of guys in the big leagues who have walks and they don't think about the walks."

There was an anxiousness in his voice when he said that -- perhaps not unlike the anxiousness he's been reported to show on the mound. The Venezuela native has had up-and-down results at Triple-A at the end of 2011 and thus far this season. He's 8-9 with a 5.50 ERA in 23 Pacific Coast League starts over that span.

"I just want to do the same," he said of his mind-set going forward. "I just want to keep working hard because I want to move up."

Mark Hamburger allowed three hits over the final two innings but completed the Express' third shutout of the season and second this month.

Round Rock scored its runs on first-inning singles by Joey Butler and Yangervis Solarte.

Express leadoff man Julio Borbon, who had his 21-game hitting streak snapped on Tuesday, went 4-for-4 to raise his average to .322.

RedHawks starter Brian Bass (1-1) was charged with both runs on nine hits over six innings.