The Nationals sent fan favorite Blevins to the Mets in exchange for the 27-year-old left-handed hitting outfielder.
The third baseman is visiting James Andrews to get another look at his left knee.
Storen faced four batters, got two outs and left the game with a trainer after issuing a walk.
Janssen said he isn't sure how long he needs to rest or when he can return to game action.
Taylor Jordan makes the start so the Nationals rotation can be aligned for the regular season.
The outfielder has been swinging a bat, throwing and sprinting only three weeks after surgery.
Set with Wilson Ramos and Jose Lobaton, the Nationals traded third-string catcher Sandy Leon to the Red Sox.
Given Casey Janssen's sore shoulder, Blake Treinen and Aaron Barrett could make the season-opening bullpen.
Janssen reported issues getting loose and shoulder discomfort during his last outing.
"We’re satisfied with what we have. We like the team we have. We like the back-ups players that we have. We like the depth that we have."