It turned out there was not a long-term injury to fear for their superstar, just some initial pain.
After getting hit by pitches in the back of the left elbow and on his left foot Tuesday, Harper is expected to play Wednesday when the Nationals conclude their two-game series with the New York Yankees.
"Oh yeah, he's in there," Martinez said.
Harper reached base four times, but it was his final two appearances that caused the most angst for the Nationals, who mustered five hits and opened the series with a 3-0 loss.
In the fifth, he dropped to the ground after being hit on the left elbow by CC Sabathia's 90.1 mph sinker. Three innings later, an 88.8 mph slider from Dellin Betances hit him on the foot and off his big toe, creating some numbness.
"I was really worried," Martinez said. "He started walking off the field. The good news is he's walking off the field, He came in a few minutes ago and said he was fine."
Harper's exit occurred on a night when the Nationals tied a franchise record by getting shut out in consecutive games for the 12th time since moving from Montreal following the 2004 season. Their scoreless drought is at 19 innings and they have eight hits in the last two games.
Harper batted third and played right field Tuesday. He batted two spots ahead of Daniel Murphy, who was 0-for-4 with two strikeouts in his season debut after missing the first 63 games recovering from right knee surgery.
Murphy started at designated hitter and will likely do so again Wednesday.
"His timing could have been off," Martinez said. "I know he's going to hit."
The Yankees opened the series by getting two homers from Didi Gregorius, who has three of their 14 multi-homer games this season. Gregorius homered at home for the first time since April 25 and is hitting .286 (10-for-35) in his last nine games after hitting .151 (14-for-93) in 22 games in May.
While Gregorius is starting to rebound from a tough month, Gary Sanchez is in a massive slump and did not start Tuesday. He is not expected to start Wednesday, giving him three days off.
Sanchez is enduring the first significant struggles of his career and spent time figuring a way out of a prolonged slump that has shrunk his batting average to .190, though the Yankees think he will get rolling again.
"The one thing he never loses is his confidence, because he's such a gifted hitter," Yankees manager Aaron Boone said before the series opener. "He wants to get in there and get it going; he expects to get it going."
He is hitless in his last 11 at-bats and is 2-for-29 with 10 strikeouts over his last seven games.
Sanchez has yet to heat up in a season when he started 2-for-36 but on May 19-21 he went 4-for-10 in two games, raising his average to a season-high .231. Since those games, Sanchez is 4-for-53.
"Maybe I'm over-thinking this a little too much, that's why I'm missing those pitches I usually don't miss," Sanchez before Tuesday's game. "I swung at some pitcher's pitches. Maybe (I'm a) little bit in between.
"But I feel good. I know if I stay healthy, it won't reflect what I should be hitting. I'm sure I'll get through this."
If Boone started Sanchez Wednesday, it would have been as the designated hitter since Sonny Gray is starting.
During the road trip, Gray allowed one run in 14 innings during wins over Baltimore and Toronto. Against teams with losing records, he is 3-0 with a 1.80 ERA but against teams with winning records, he is 1-4 with a 7.61 ERA in five outings.
Last Wednesday, Gray turned in his first scoreless start since becoming a Yankee when he allowed two hits in eight innings during a game that Yankees won in the 13th.
Gray made two starts for Oakland Athletics against the Washington Nationals. In those outings, he allowed six runs on 10 hits in 14 innings.
Since Jeremy Hellickson and Stephen Strasburg are on the disabled list, Washington has an opening in its rotation for Wednesday and it will be filled by Erick Fedde, who will be called up from Triple-A Syracuse for his second start this season.
Fedde allowed three runs on five hits in 5 2/3 innings as a fill-in starter against the San Diego Padres on May 23. Fedde is 0-2 with an 8.14 ERA in four career starts for the Nationals.