Doug Fister threw two innings at extended spring training on Thursday and "assuming all goes well" he could join the Washington Nationals in about three weeks, according to Matt Williams.

Fister is on the disabled list retroactive to March 23 with a strained back muscle.

"We've got to build him like we would build him in spring. I think he's a little bit ahead of the game in that regard, but certainly would like him to get five innings somewhere, at least," Williams said.

The Nationals acquired Fister in a trade from the Detroit Tigers in the offseason.