Rookie right-hander Chad Bettis gets a sixth chance at a first major league victory on Tuesday night when the Colorado Rockies host the San Francisco Giants in the middle game of a three-game series at Coors Field.

A 24-year-old from Texas, Bettis debuted with the Rockies on Aug. 1 and allowed five runs in six innings of an 11-2 loss to the Atlanta Braves.

No-decisions against the New York Mets and Pittsburgh followed, before he was roughed up for eight runs in 2 2/3 innings against Baltimore while taking an 8-4 loss on Aug. 17.

His most recent outing, at Philadelphia on Aug. 22, saw him surrender just a run on six hits in 5 1/3 innings of a game the Rockies ultimately lost, 5-4.

Colorado has been outscored in his five starts, 29-15, losing four.

Giants journeyman right-hander Yusmeiro Petit makes his first start of the season and the 38th of his career across parts of six seasons.

The Venezuelan was called up from Triple-A Fresno to take the spot of injured starter Matt Cain after posting a 4.52 earned run average in 15 starts in the minors.

He threw 5 2/3 innings of relief in his lone big-league appearance of 2013, allowing two runs on six hits in the Giants' 9-3 loss to Cincinnati on July 23.

In four career meetings with the Rockies, Petit is 0-1 with a 7.00 ERA in 18 complete innings.

On Monday, Todd Helton hit a two-run home run and Juan Nicasio pitched six shutout innings as the Rockies took a 6-1 win.

Nicasio (8-6) gave up just four hits and two walks while striking out nine for the Rockies, who have won three of their last four.

Charlie Blackmon hit a solo homer and drove in two while Nolan Arenado added three hits and two runs scored in the win.

Barry Zito (4-10) continued to struggle as he remained winless over his past 16 appearances. He pitched four innings and was touched for five runs on nine hits to drop his second straight start for the Giants, who were coming off a split of a four-game series with Pittsburgh.

The Giants won seven of the first 13 games with the Rockies in 2013, though Colorado took two of three when they let met, from June 28-30, at Coors Field.