PITTSBURGH -- If Mitch Keller's afternoon was going to end on his own terms, Ben Gamel needed to get on his horse.

With two outs in the top of the fifth inning, Eric Hosmer smacked a slicing line drive. If the ball touched grass, Hosmer would’ve had extra bases. Keller likely would’ve been pulled.

But Gamel had Keller’s back. He tracked the ball, he laid out, and he hauled it in. Inning over. Outing over. As he walked to the dugout, Keller let a smile escape him.

Keller penned his best start of the young season, allowing one run across six innings with five strikeouts to no walks in the Pirates’ 5-2 loss to the Padres on Sunday at PNC Park. Following an encouraging yet forgetful first month, maybe this was the outing that gets Keller’s season truly rolling along.

“He was strong,” said manager Derek Shelton. “His velocity maintained throughout the game, and in fact it started to continue to tick up near the end, and just like two starts ago, he threw the ball really well. We just didn't score any runs while he was in the game. He gave up one, but I thought he threw the ball really well.”

That Keller pitched well against San Diego is no small feat. Even without Fernando Tatis Jr., who is still out after undergoing wrist surgery in March, the Padres have featured one of baseball’s best offenses. Manny Machado, to his credit, has been amon the best players in baseball through one month.

San Diego gave Keller some fits in the third inning, the frame in which he allowed his lone run, but other than that, Keller was in control -- in the end, becoming the first Pirates pitcher so far this season to log six innings.

“It means a lot,” Keller said. “It means that the pitch count was low. It means I was filling up the zone and getting outs. Whenever you can go six is a great thing.”

Along with neutralizing San Diego’s offense, Keller was able to go six innings because he eliminated walks, his most significant area of growth thus far. Including Sunday, Keller has already had two starts this season in which he didn’t allow a walk. For comparison, Keller only had three such games last season. It should come as no surprise, then, that Keller’s 2.66 walks per nine innings is on pace to be the best mark of his career.

“It all stems from the work I did this offseason, just getting me in better spots, better positions, more comfortable, more confidence,” Keller said. “When you add up all those things it usually adds up to more success in the zone and better command. Right now, I feel like I can throw the fastball whenever I want to.”

Another reason that Keller was able to log six innings was his ability to hold the Padres in check his third time through the order, a point in the game that has historically been a problem.

Entering play, opponents had a career slashline of .379/.443/.578 when facing Keller for a third time. On Sunday, Keller retired all five batters he faced in his third time through the lineup. Against Jake Cronenworth, Keller reared back on his 75th pitch of the afternoon to throw a 99.7 mph fastball, one that generated a routine groundout.

On the subject of velocity, Keller continued to maintain his upper-90s heat well into an outing. In the first inning, Keller threw 11 fastballs, with an average velocity of 96.5 mph. In his sixth and final inning, Keller threw four fastballs, with an average velocity of 97.7 mph. That will always play.

“The fact that his velocity maintained throughout the game was something that was very impressive,” Shelton said.

April wasn’t the breakout month that Keller hoped for following a phenomenal Spring Training, one in which he rediscovered his velocity. Keller’s fastball was indeed back, but through four starts, he had a 6.62 ERA. The results weren’t there, but the advanced numbers -- xERA, xFIP, average exit velocity -- suggested better days were ahead.

As the calendar has flipped from April to May, maybe those better days are arriving.