He lost his one decision in two starts this season at Chase Field, allowing 11 earned runs on 15 hits in 11 innings, a 9.00 ERA. He also started April 24, a 7-6 loss, allowing seven runs on eight hits that night in six innings. He gave up four runs on seven hits in five innings Saturday.
On April 19, he shut out the D-backs over eight innings on three hits at San Diego in a 1-0 win.
How to explain the dichotomy?
"I've been more comfortable this year at Petco," Chacin said before the Padres played their final game at Chase Field this season Sunday. "It's hard to explain it. For some reason when I have problems, it always happens on the road."
Chacin pitched four effective scoreless innings Saturday, working out of a bases-loaded situation when D-backs starter Zack Godley struck out to end the second. But in the fifth, Arizona tallied five singles to score four runs.
That was it for Chacin, who was lifted at the 100-pitch mark.
"I thought in the first four innings, Jhoulys was in typical battle mode for himself," Padres manager Andy Green said. "It wasn't perfect. It wasn't pretty. He wasn't very pitch efficient. In the fifth, the hits he gave up included a fister to [Paul] Goldschmidt, a fister to J.D. Martinez. They were on good pitches. It skewed his line drastically and made it look like he didn't throw the ball as well as he did."
Overall, Chacin, 29, has had a nice bounce-back season in San Diego. He's 12-10 with a 4.06 ERA in 29 starts, the most games he's started since he was 14-10 with a 3.47 ERA in 31 starts for the Rockies in 2013, by far his best of nine big league seasons.
He'd have had a much better season had it not been for the road woes.
"It didn't matter how I pitched on Saturday night," he said. "We came back and won the game. That's the only thing that's important."
Barry M. Bloom is a national reporter for MLB.com and writes an MLBlog, Boomskie on Baseball. Follow @boomskie on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.