Jeremy Hellickson is headed to the 10-day injured list with a strained right shoulder. (Patrick Semansky/AP)

NEW YORK — The Washington Nationals added newly signed pitcher Javy Guerra to the 40-man roster and activated him Tuesday afternoon. To make room on the 25-man roster, the team moved starter Jeremy Hellickson to the 10-day injured list with a strained right shoulder.

Hellickson was long tossing on the field a few hours before the Nationals’ 7:10 p.m. game against the New York Mets at Citi Field, however. Manager Dave Martinez and Hellickson said throwing is permitted while he is on the IL, and Hellickson added that this is a chance for him to avoid the wear of full outings. He has been dealing with shoulder pain since spring training, and while it hasn’t gotten worse, it hasn’t improved. Washington is hoping the next 10 days or so will help Hellickson reach 100 percent.

Asked why he went on the IL now, rather than earlier in the season, Hellickson noted that daily treatment has not led to the desired improvements. He doesn’t expect this trip to the IL to last longer than 10 days.

“That feels good," Hellickson said of throwing from about 200 feet Tuesday. “It’s just taking a start off to give it some rest, and not that big workload on a start day. I can take one of those off. It’s just on and off. It feels good one day, not so good the next. So give it some rest and hopefully get back to 100 percent.”

In addition to swapping Hellickson and Guerra, the Nationals are signing right-handed pitcher Kevin McGowan to a minor league deal and sending him to Class AAA Fresno, according to a person with knowledge of the situation. McGowan, 27, is a career minor leaguer and most recently pitched in the independent Atlantic League.

The Nationals signed Guerra on Monday, and he was at home playing with his 2-year-old son in Toronto when he heard the news. The nine-year veteran has a career 3.44 ERA with five teams. A long reliever, Guerra went more than one inning in four appearances and was serviceable for Toronto this season, posting a 3.86 ERA over 14 innings. Guerra was designated for assignment on April 18, had his contract selected by the Blue Jays on May 10 and was again designated for assignment Saturday. The Nationals, in search of trustworthy relievers, claimed him off outright waivers.

“I was just hanging out,” Guerra said. “And then, before you know, you find out that you have to get down here and get ready to play tomorrow.”

Hellickson has struggled this season, with a 6.23 ERA through eight starts, but he did not mention shoulder discomfort after his most recent appearance Sunday night at home against the Chicago Cubs, when he allowed three runs in three innings. He has had command issues, issuing 10 walks over his past three appearances, and Washington is 3-5 in games Hellickson has started.

Washington is now without its fourth and fifth starters; Aníbal Sánchez is on the IL with a strained left hamstring and Erick Fedde is starting in his place against the Mets on Tuesday. Sánchez could throw a simulated game at Nationals Park this Friday, and Martinez is confident he could return soon. As for filling Hellickson’s spot this Friday, the Nationals have not yet made a decision. Kyle McGowin is a logical option and, having last thrown Sunday, could be on regular rest. Martinez counted him as a possibility to face the Marlins for his second career start.

LINEUPS

Nationals (19-28)

Trea Turner, SS

Adam Eaton, RF

Anthony Rendon, 3B

Juan Soto, LF

Gerardo Parra, 1B

Victor Robles, CF

Brian Dozier, 2B

Yan Gomes, C

Erick Fedde, P

Mets (21-25)

Jeff McNeil, LF

Amed Rosario, SS

Robinson Cano, 2B

Pete Alonso, 1B

Todd Frazier, 3B

Wilson Ramos, C

Carlos Gomez, RF

Juan Lagares, CF

Zack Wheeler, P

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