Johnson said that pitching coach Steve McCatty and general manager Mike Rizzo were "raving" about Detwiler's session but that the team wants to make sure Detwiler doesn't suffer any setbacks overnight. Should that happen, right-hander Ross Ohlendorf would start in his place.
Ramos, who began his rehab on Friday and Saturday, catching for the Nationals' Gulf Coast League affiliate, caught seven innings and went 0-for-4 in a rehab appearance for Class A Advanced Potomac on Monday night. If no problems surface, the next step would be for him to catch nine innings. He also could appear in a game at designated hitter in order to get extra at-bats.
Ramos has been on the disabled list since May 16 with a strained left hamstring. He is scheduled to return on Saturday but could make it back as soon as Thursday.
Andrew Simon is a reporter for MLB.com. Follow him on Twitter @HitTheCutoff. This story was not subject to the approval of Major League Baseball or its clubs.