Ross Ohlendorf. (Doug Pensinger/Getty Images)

Ross Ohlendorf has served his role well for the Nationals this season. He has a 2.98 ERA over 48 1/3 innings. The Nationals have won all five of his starts this season, including the past three as a full-time member of the starting rotation. But the past two starts have required no small measure of sweat and effort. And following his start on Sunday, Manager Davey Johnson again raised concerns about the right-hander’s endurance.

As he had last week, Johnson raised the possibility of starting rookie right-hander Tanner Roark when Ohlendorf’s spot in the rotation comes up next on Saturday. With extra arms called up from the minors with the expanded rosters, this may be Johnson’s best chance to do it. Ohlendorf completed five innings on Sunday, but coughed up nine hits, several loud outs and four runs on 79 laborious pitches. Six of the nine hits were for extra bases.

“Around that 70-80 pitch mark, I start getting a little queasy,” Johnson said. “Fact is, [third base coach] Trent [Jewett] was looking at me, giving me the sign, are you pinch-hitting for him after four. I had to give him a no.”

Johnson wrestled with the idea of starting Roark instead of Ohlendorf even before Sunday’s start. In his previous start, Ohlendorf’s velocity dropped by a handful of miles per hour in the final inning, “batting practice” pitches which the right-handed starter said were intentional. Johnson, however, at first thought Ohlendorf was tiring. Ohlendorf’s velocity was stronger on Sunday, but still had fluctuations.

His fastball sat between 92 and 95 mph in the first inning. Two innings later, it was between 86 and 93 mph. In the fourth, Ohlendorf’s fastball ranged as low as 88 mph to as high as 96 mph. But the changes didn’t haunt him as much as his location. Many of Ohlendorf’s pitches were up in the strike zone, often belt-high. And when he left his hard fastballs up, the Mets clobbered the ball. Even the outs were hard liners or deep flyballs, but most loud cracks of the bat.

“That’s the worst my command’s been I think all season,” he said. “I don’t expect that to carry over for the next one. I feel like I’ll make some adjustments. My command just wasn’t good.”

To his credit, Ohlendorf managed to pitch around many of the hits by inducing groundouts. After four innings, the Nationals trailed only 3-2. Johnson joked that Ohlendorf looked gassed. (“I have to tell ya, I’ve never seen a human being sweat so much,” he said.) But Ohlendorf said his endurance was not an issue.

“I felt the same the whole time,” he said. “I felt like I was actually pitching a little bit better towards the end. The first inning I felt like was the worst.”

Johnson had been wanting to give Roark, who has been impressive as a long reliever this season, the chance to start so the Nationals could evaluate him. Roark, a sinkerballer, has a 1.19 ERA over 22 2/3 innings. According to Johnson, Ohlendorf doesn’t recover as quickly. So if he does flip the two pitchers’ roles, he may be without Ohlendorf as a long reliever for a few days. “But now that we have more guys in the ‘pen, it might be easier to make that move,” he said.