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Left-hander Ross Detwiler threw 3 2/3 innings in a rehab assignment at Class A Potomac this afternoon, allowing Frederick one run on seven hits, walking none and striking out four.

The Nationals expect the outing to be Detwiler’s final tune-up before he returns to the rotation. Detwiler has been on the disabled list retroactive to May 16 with a strained right oblique.

In eight starts before he strained his oblique, Detwiler punched up a 2.76 ERA with 23 strikeouts and 10 walks in 45 2/3 innings.