The Washington Nationals placed right-handed reliever Ryan Madson on the disabled list with a sore pectoral muscle after Sunday’s loss to the Dodgers. Madson was unavailable to pitch Saturday and Sunday because of what Manager Dave Martinez described as a muscle-related pain in his chest. The 37-year-old appeared in 21 of the Nationals’ first 42 games, and Martinez said the problem popped up a few days ago.

“It was a couple days ago so we’ve been keeping an eye on it. He said he felt a little better,” Martinez said. “But just to be safe, we want him healthy.”

Madson is the first Nationals reliever to succumb to the extreme workload many have had to endure this season. Sammy Solis, who allowed a home run Saturday night, appeared in 25 of the Nationals’ first 45 games. Brandon Kintzler appeared in 23 of 44. The Nationals have established a problematic propensity for playing close games. Their 15 one-run games entering Sunday were third-most in the National League. Dave Martinez has yet to find reliable options behind his big three relievers. His Nationals trailed by just one entering the eighth inning Sunday, but after Wander Suero and Shawn Kelley struggled through an inning each, they trailed by five.

Without him, the Nationals lack their best setup man for Sean Doolittle and their firefighter used by Martinez in a variety of situations besides the ninth. They will need to replace him, and given the workload thrust on Solis’s already fragile left arm, veteran left-hander Tim Collins seems likely to get the call. Collins, who the Nationals signed to a minor league deal two years ago when he was still rehabbing from a second Tommy John surgery, has a 3.63 ERA in 17 appearances for Syracuse this season. He was a staple of the solid Kansas City Royals bullpens before injuries slowed him down.

Former Colorado Rockies right-hander Justin Miller could also be a candidate. The 30-year-old made eight scoreless appearances in Class AAA Syracuse entering Sunday and owns a 4.99 ERA in 82 big league games. Miller’s minor league deal includes an opt-out date of June 15, but he is out of options and is not on the 40-man roster. He also pitched an inning Sunday, which does not necessarily preclude him from promotion. Other options include right-hander Austin L. Adams, who struggled with command in his big league stints. But as of late Sunday, all signs from those familiar with the Nationals’ decision-making process pointed to Collins being the likeliest choice.

None of them can replace Madson, whose 4.19 ERA in 21 games does not illustrate his importance or effectiveness. The timetable for his return is not yet known, though the disabled list stint will be backdated to May 17. The Nationals owe Madson $7.6 million this season, the final year of a three-year deal they inherited when they acquired him from the Oakland Athletics last season.

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