That ERA has slowly crept up as the season has progressed, and now stands at 3.49 after allowing four earned runs in five innings of a 5-0 loss to the Mariners on Wednesday.
"In May, I think I've missed too much pitches up in the zone and my fastball command in my last three starts before this one hasn't been very good," said Senzatela, who was handed his first loss in May on Wednesday. "I need to try and do a good job next month."
In what was a disappointing month for Senzatela, a sensational start against the Cardinals -- where he tossed eight scoreless innings and scattered five hits -- on May 26 pointed to Senzatela's form in April.
A three-run second inning on Wednesday -- in which Danny Valencia and Mike Zunino each pasted RBI doubles -- and a lack of control in a one-run fifth when he walked two batters and advanced two runners with a balk and a wild pitch, marred what Senzatela believes was still an encouraging start.
"I feel good today, [with] my fastball command, good slider," Senzatela said. "They hit me. I threw a couple of fastballs up and can hit."
He posted a career-high seven strikeouts on Wednesday, due in part to an improved out-pitch in his slider. He finished three of the seven at-bats that resulted in strikeouts with his go-to secondary pitch.
"I feel more confidence and that was working really good tonight," Senzatela said of his slider. "I'm working to strike out people and my secondary stuff, that helped me tonight."
The Rockies run support helped keep Senzatela afloat in less-than-stellar outings. Colorado averaged 9.6 runs in Senzatela's last five starts entering Wednesday's contest.
That's a significant reason why Senzatela was knocking on the doorstep of Dallas Keuchel's Major League lead in wins with eight, despite regressing with a 3.60 ERA in his last four starts coming into Wednesday's contest. Senzatela wasn't as fortunate against the Mariners, as a combination of starter James Paxton and Seattle relievers blanked the Rockies.
Josh Horton is a reporter for MLB.com based in Seattle. He covered the Rockies on Wednesday.