Kimball, recovering from rotator cuff surgery last July, was 1-0 with a 1.93 ERA over 14 innings with the Nationals in 2011.
He has appeared in two games so far at low Single-A Hagerstown and the Gulf Coast Nationals. During his rehab assignments, Kimball has gone two innings without allowing a run, with just two hits, no walks and three strikeouts.
Update: Kimball fired two scoreless innings, allowing two hitters to reach on an error and hit batsman. He threw 26 pitches, 19 for strikes. He struck out one hitter and allowed no hits, inducing three flyouts and three groundouts.