Jayson Werth Alex Brandon/AP

Nationals right fielder Jayson Werth could spend roughly two more weeks on the disabled list after an MRI exam today revealed a more significant strain in his hamstring than originally thought, Manager Davey Johnson said.

“I got kind of an alarming report from our doctor that said he was going to be a while longer,” Johnson said. “I think he was rushing it. He started to realize that hamstrings take a little more time. Something happened to him like it happened to Wilson Ramos. So we’ll take a step back on him.”

Werth last played May 2 and tonight will miss his 16th game with a right hamstring strain. Werth, who was hitting .260 with a .308 on-base percentage and a .400 slugging percentage before the injury, visited a specialist in New York last week after he played in a rehab assignment Wednesday at Class A Potomac.

“When I played in Potomac last week I felt my hammy grab on my first [at-bat] when I left the box on the groundout,” Werth said in an e-mail. “Didn’t think it was too bad, so I stayed in the game. As [the] game went on it was apparent I wasn’t ready, so I exited game early.

“The next day I went to NYC to see my personal [doctor and] trainer for treatment. It was apparent to all more time was needed to heal. MRI confirmed today what I already knew.”

Without Werth, the Nationals have relied on a combination of Tyler Moore, Roger Bernadina and Steve Lombardozzi in the corner outfield spots. The trio has also filled in for Bryce Harper, who is returning tonight after he missed two games with swelling in his left knee, an effect of running into the Dodger Stadium wall a week ago tonight.

Originally, the Nationals and Werth expected he would miss only a few games – they did not place him on the disabled list until he had sat for nearly a week. Werth was also dealing with a bruised ankle and a stomach flu at the time, which Johnson said may have obscured the severity of his hamstring injury.

“There was that mix-up – was it caused by dehydration, or did he really hurt something?” Johnson said. “We never could figure that out. But obviously, he does have a strain in hamstring. It’s going to take some time.”

Werth, who turned 34 today, is in the third season of a seven-year, $126 million contract. Last year, he missed 75 games after he broke his left wrist attempting to make a sliding catch and played in 81 games all season. Werth could miss roughly 30 games before he makes his return from his current hamstring injury.