"He's in the lineup. He's good to go," Martinez said. "It's good to have him back in there. He said he didn't feel anything really. I think he just cramped up. We don't want to take a chance."
Martinez said the training staff was concerned it was something worse when Soto was hurt during batting practice.
"He took swings in the cage before the game," Martinez detailed. "He bent over and he locked up. When your 20 in the spot that he had it you right away think it could be an oblique. We just wanted to be careful."
Update: About one hour before first pitch, Soto was scratched from the lineup with back spasms for the second straight game. Adam Eaton moves to left field, Michael A. Taylor will play center field and Victor Robles will play right field.
Positive news on the recovery of shortstop Trea Turner from a broken right index finger. Turner has been out since April 3. Martinez said Turner could start baseball activities by Sunday. The former N.C. State star will be on the road trip beginning in Philadelphia.
"He will travel because he's doing everything," Martinez said. "He's running, he's exercising. I think this week he might even take a couple of swings. He's doing way better. Hopefully, by the end of this week, he could start probably swinging a bat.
"He's healing. The question is now getting him ready to play baseball, getting him out and getting him some at-bats. It's almost like he's got to start spring training all over again."
Martinez said the Nationals are giving rookie Carter Kieboom a day off. The 21-year-old shortstop has made six starts in a row is batting .136 with two homers and nine strikeouts.
"I talked to him this morning. I had a great conversation with him," Martinez said. "I told him we're just going to give you a little mental break today. We assured that he is doing fine. He's 21. I told him, 'You're 21, you made the major leagues, that's pretty impressive.' He wanted to get some work in with (Tim) Bogar today and he's going to go hit and I said he will be right back in there tomorrow. And if we need you sometime today be ready because you'll definitely be used. We'll still give him a little day."
In West Palm Beach, Fla., right-handed reliever Trevor Rosenthal is healthy and working on improving his mechanics and strike zone command.
"Fine, yeah. Talked to him today. He's doing well," Martinez said. "He's got a long toss routine, threw a bullpen the other day. It was really, really encouraging. We are going to take it step by step. They put him on a pretty good plan and we're going to stick to that plan and we'll see where he's at."
Right-handed reliever Austen Williams had a significant bullpen session this week in Florida. He is out with a sprained right AC joint.
"He threw 40 pitches the other day and threw very well," Martinez said. "He is still at West Palm. Just try to build him up, see how he feels and go for there."
Right-hander Erick Fedde's pitching turn arrives Friday for Double-A Harrisburg. Fedde tossed four shutout innings to help get the Nats back in the game on April 28 in a 7-6, 11-inning win over San Diego. Martinez said the Nationals will decide later today if Fedde will start tomorrow night for Senators or come out of the bullpen. He is the serious candidate for the role of long man and spot starter for the Nats.
"We haven't thought about it yet," Martinez said. "We're going to talk about it today after the game, whether to start him or let him come out of the bullpen."
Harrisburg has right-hander Will Crowe (3-0, 0.96 ERA) listed as its probable starter for Friday night's game against Trenton.
Update II: The start of today's game is being delayed by inclement weather.
Update III: The game is expected to begin at 6:30 p.m.