Matt Slocum / AP Matt Slocum / AP

Jayson Werth is set to land on the 15-day disabled list not out of pain but out of caution and team need. He has been battling cramping in his hamstring since April 29. He hasn’t played since May 2. Eury Perez is expected to arrive in Washington on Saturday from Class AAA Syracuse to take his place on the active roster.

“I feel bad the team has been playing with 24 guys for over a week now,” Werth said following Friday’s 7-3 win over the Chicago Cubs. “We feel like we’re close and I feel like it’s really not that severe. But it’s one of those things you go out there with the way it is and you might make it severe pretty quickly. Erring on the side of caution but at the same time at this point I think it’s necessary.”

The Nationals will likely make the move official on Saturday and backdate Werth’s disabled list stint to May 2, the last game Werth played. Both he and the Nationals believe he will be ready to reactivated on May 18, the first date he would be eligible. So it will be a short stint on the disabled list.

Werth’s MRI results on Thursday were relatively clean. Werth has felt cramping mostly, but not exclusively, in his right leg. The Nationals and he believe dehydration stemming from a stomach bug is at the root of the cramping. He is taking antibiotics for the stomach bug.

“The thing about it for me is that I’ve never had a hamstring issue or injury or really anything,” he said. “We’re kinda in uncharted waters as far as that is concerned but at the same time there is some dehydration and some cramping issues going on.”

Werth has tested his hamstring by stretching, running and hitting this week, all which haven’t been an issue. The cramping has persisted. He won’t stop all activities while on the disabled list and will continue test his hamstring. Towards the end of next week, he wants to play on a rehab assignment before he can be reinstated.

“The most frustrating thing about the whole thing is I feel pretty good,” Werth said. “I was out there running the last couple days. I’m running good. It’s just a little cramp there at times and cramps lead to bigger and worse injuries. Just being cautious and Davey [Johnson] is being cautious the whole time. He keeps saying he doesn’t want to lose me so I think we’re at the point we have to make the decision.”