"I thought Mazzaro pitched really well, he really limited the damage in the third and in the fourth, really," manager Ned Yost said. "He mixed his pitches well."
The Rangers bunched four straight hits, including Mitch Moreland's homer, against Mazzaro in the fourth.
"I was just leaving the ball up a little too much, leaving the ball over the plate, trying to be too perfect," Mazzaro said. "I kind of got too relaxed out there."
Mazzaro has a 5.84 ERA and has given up 19 hits and five walks in 12 1/3 innings. O'Sullivan has a 3.24 ERA and has given up nine hits and three walks in 8 1/3 innings.