Stephen Strasburg, prone to heavy sweating on the mildest of days, had turned a bright red shirt to a much darker shade by the time he threw 50 pitches in the brutal heat and humidity Friday afternoon. With General Manager Mike Rizzo, Manager Dave Martinez and other Washington Nationals officials watching closely, the right-hander inched closer to his return to the rotation by throwing to hitters (Pedro Severino and Matt Wieters) without any problems.

He is scheduled to make a rehab start Tuesday, though all of the Nationals’ affiliates are either off or on the road, meaning the team will have to get creative. Martinez said Strasburg probably will require two such starts — one Tuesday and one presumably five days later — before returning to the rotation. If Strasburg pitches Tuesday and again five days later, he would be on regular rest to start the Nationals’ first game after the all-star break, a crucial home matchup with the Atlanta Braves. Everything has to go right between now and then, of course.

“If he feels fine, he’ll go out Tuesday, and we’ll see how he feels then and then maybe one more,” Martinez said. “But very encouraging. He looked very good.”

Strasburg has been out since early June, when inflammation in his throwing shoulder forced him from a start. By the time he returns, he will have missed about six weeks, a stretch in which the Nationals’ rotation has been deeply affected by his absence. At the time of Strasburg’s injury, the rotation had the second-lowest ERA in the National League. Since, they have the worst ERA in the majors at 6.62.

Another right-hander, Joe Ross, has been out since last July, when he underwent Tommy John surgery. Ross has spent most of this season rehabbing at the Nationals’ facility in West Palm Beach, Fla., but he rejoined the team this week and threw 25 pitches in that same simulated game. He is a long way from returning but said he will be able to make an impact this season in some capacity.

“Wherever I can fit in, especially in September hopefully with extended rosters, as long as I can hopefully get out there and throw some innings, I’ll be happy,” Ross said. “That’s really what I’m working toward.”

Had he been healthy, Ross probably would have been the Nationals’ fifth starter. Without him, Washington auditioned Jeremy Hellickson, who has fared well with the exception of his rough outing Thursday night. Hellickson pitched that game despite a virus that left him ill again Friday, the same one that knocked Spencer Kieboom out of commission for days and left Shawn Kelley seeing spots on the mound at one point last week. Martinez said the staff has disinfected the clubhouse, hoping to prevent the virus from spreading. Kieboom said it took him days to recover, though he is making his first start Friday night since the virus struck, catching Gio Gonzalez.

Gonzalez has struggled working with Severino, seemingly out of sync. Martinez said Kieboom playing has more to do with getting Severino a rest, but with Gonzalez pitching to a 9.31 ERA over his past five starts, allowing opponents a .321 batting average against and averaging fewer than four innings in each, a change might be worth a try.

WASHINGTON NATIONALS (43-43)

Trea Turner SS

Juan Soto LF

Anthony Rendon 3B

Bryce Harper CF

Matt Adams 1B

Adam Eaton RF

Wilmer Difo 2B

Spencer Kieboom C

Gio Gonzalez P

MIAMI MARLINS (36-53)

Starlin Castro 2B

Brian Anderson RF

J.T. Realmuto C

Martin Prado 3B

Justin Bour 1B

Garrett Cooper LF

Miguel Rojas SS

Cameron Maybin CF

Dan Straily P