Elbow inflammation suffered during spring workouts has forced the Washington Nationals to keep newly-acquired starting pitcher Doug Fister on the shelf so far this season. He might not be on the shelf for much longer, however.

During an interview on MLB Network Radio, Nationals manager Matt Williams claimed that Fister will make one more rehab start before taking his spot in the team’s rotation on May 7:

Williams “Friday is hopefully [Fister's] last rehab start & if all goes well, he’ll be scheduled to have his 1st start the 7th or 8th”

— MLB Network Radio (@MLBNetworkRadio) April 30, 2014 

The Nationals acquired Fister from the Detroit Tigers in December  for infielder Steve Lombardozzi, lefty reliever Ian Krol and lefty starter Robbie Ray (who will make his big league debut next Tuesday). The trade caused some to scratch their heads, as Washington really didn’t give up all that much for a quality veteran starter. Of course, Ray could turn into a very good starter with some experience.

Fister boasts a career ERA of 3.53 (115 ERA+) along with high groundball rates due to an increased use of his sinker. While he doesn’t throw hard, Fister throws a particularly “heavy” ball that drops out of the zone and causes hitters to make weak contact.

The 30-year-old will add some much needed depth to Washington’s rotation. Headlined by the trio of Stephen Strasburg, Jordan Zimmermann and Gio Gonzalez, the rotation weakens significantly after. Tanner Roark has been surprisingly consistent, but there’s no telling the type of contributions he’ll be making a month or two from now.

Taylor Jordan made five starts before the team sent him down to the Syracuse Chiefs, so it’s clear that the addition of Fister would go a long way to shoring up this rotation.

If he stays healthy, Fister will provide the Nationals with yet another quality arm. That makes four—Strasburg, Gonzalez and Zimmermann being the other three. This is the type of rotation that can make a postseason run in a tight National League East. It’s a rotation that can compete with the Atlanta Braves and their minuscule 2.32 ERA amongst starters.

But, first things first.

Fister will need to prove his health during his rehab start before getting the call. The game on May 7 is an afternoon affair at home against the Los Angeles Dodgers, a team that he has never faced in his six-year career.