CINCINNATI -- When swingman Nick Martinez gets chances to start for the Reds, regardless of how they come his way, he would prefer to make the most of them.

Martinez has made three starts this season, but hasn't found the same groove that he's shown as a reliever. A four-run third inning was his undoing during Thursday's 5-0 loss to the Phillies at Great American Ball Park.

“Keep pushing forward. I’m not far off from getting on a roll I feel like," Martinez said. "From a starting standpoint, I’m running into some big innings. There’s a lot of good to take away from my starts. One or two pitches that I don’t execute, it always seems to [be] with guys on base that lead to a big inning.”

The top of the third inning opened with Nick Castellanos hitting a leadoff single and scoring on Bryson Stott's RBI triple. With one out, Kyle Schwarber drove in Stott with a sacrifice fly.

A first pitch cutter to Trea Turner was hit to deep center field for a ground-rule double. Next was Bryce Harper -- who returned after missing three games on the paternity list -- who hit a 2-2 changeup left over the middle of the plate for a two-run homer to right field to give the Phillies a 4-0 lead.

“It was a little combination of bad luck and missed locations to the wrong guys," Martinez said.

Four of Harper's five homers this season have come against Cincinnati, making him definitely the wrong guy to miss with location.

“He’s one of the best in the game, if not the best," Martinez said. "I like the pitch call. I missed the execution and he capitalized. Same with Turner, he hit the cutter for a double. That’s another good hitter where I didn’t execute the pitch.”

Overall, Martinez pitched six innings, allowing five earned runs on 11 hits. He didn't walk a batter and struck out three. As a starter, he is 0-1 with a 7.31 ERA.

Martinez, who was signed to a two-year, $26 million free agent contract on Dec. 1, opened the season in the rotation while Nick Lodolo was on the injured list. He made two starts before moving to the bullpen and gave up only one earned run over seven innings in two appearances, including three scoreless innings on Saturday vs. the Angels.

When Frankie Montas was struck on the arm by line drive on Sunday and went on the IL, Martinez slid back into the rotation for what is expected to be two starts.

“I think I do and we do a good job here of preparing for that and communicating really well," Martinez said. “I would not say it had anything to do with going to the bullpen and coming back into the rotation and going back to the bullpen, whenever that may be. In terms of preparation, it’s great. My body feels good. Probably I need to be a little bit better with two strikes.”

• How the Reds plan on utilizing Martinez

The Reds lineup managed just one hit over six scoreless innings against Phillies ace Zack Wheeler. Following a leadoff walk by Jeimer Candelario in the third, Santiago Espinal hit a single to put runners on the corners.

Wheeler shut down the rally by notching back-to-back called strikeouts on Luke Maile and Will Benson. Elly De La Cruz's walk loaded the bases with two outs, but Spencer Steer's fly ball to the right field warning track was caught by Castellanos to end the inning.

By the end of the day, Steer's slump reached 0-for-18.

“We started to get to Wheeler there that one inning. We made it tough on him,” Reds manager David Bell said. “We get a hit there, we’re able to break through and maybe it’s a different game. Give him credit. He didn’t allow us to do that.”

The Reds split the four-game series vs. the Phillies, but had taken the seven-game season series from them with Wednesday's 7-4 win. The homestand ended at 5-2 before the Reds head out on a six-game road trip at Texas and San Diego.