NEW YORK -- Jeremy Hellickson’s shoulder has been bothering him since Spring Training, a lingering injury he said has not shown much improvement or grown much worse in the ensuing months as he continued to pitch through it. At least until Tuesday, when he and the Nationals finally decided to take some time to get the injury right, placing Hellickson on the 10-day injured list (retroactive to Monday) with a right shoulder strain, which manager Dave Martinez referred to as “tendinitis.”

Washington activated right-hander Javy Guerra, who was claimed off waivers from the Blue Jays on Monday.

“It hasn’t gotten better,” Hellickson said. “We’ve been treating it every day. It hasn’t gotten better. We’ll see what rest does.”

Except the plan for Hellickson does not appear to include much rest. Less than an hour after the team announced Hellickson would be sidelined with the shoulder injury, he was in center field playing catch before Tuesday night’s game at Citi Field, backing up enough to stretch out his arm for long toss.

It was odd considering Hellickson said the injury has felt fine during starts but has bothered him in between outings, especially when he wakes up. Still, Hellickson did not plan to take much actual time off from his normal routine, believing his arm would recover without the workload required to start every fifth day.

“I feel like it’s not going to be more than a 10-day thing, so I don’t want to get too far behind,” he said. “Just taking a start off and taking that one day of 80-90 pitches off should help and get me back closer to 100 percent.”

Hellickson’s stint on the injured list comes after one of his roughest outings of the season this past Sunday against the Cubs, when he battled his command from the beginning, lasting just three innings and allowing three runs, including a home run. He has been far from the consistent fifth starter the Nationals hoped they brought back as a free agent last winter, posting a 6.23 ERA with 30 strikeouts and 20 walks in 39 innings in nine outings (eight starts) this year.

Hellickson, however, did not want to use his injury as an excuse for his slow start.

“I felt good when I was out there,” Hellickson said. “It maybe affected my command a little bit. But I felt fine. I felt fine when I was out there. I don’t think it affected too much.”

Despite his struggles, his absence is a blow to this Nationals rotation, which is now without its No. 4 and No. 5 starters in Hellickson and Aníbal Sánchez, who is also on the IL with a left hamstring strain. The good news for Washington is Sanchez threw a bullpen session Tuesday at Citi Field and is scheduled for a simulated game Friday, the same date of Hellickson’s next scheduled start. If all goes well, Sanchez would almost certainly slot into Hellickson’s spot in the rotation for now.

As far as Hellickson’s replacement in the rotation, Martinez said the team is considering right-hander Kyle McGowin as a candidate to take his place Friday night against the Marlins at Nationals Park. The Nationals’ options are somewhat limited, though. Erick Fedde, who started Tuesday night, has already been moved from the bullpen back into the rotation to start in place of Sanchez, and Joe Ross would likely require a Minor League rehab stint to get his stamina built back up.

“Hopefully this is a short-term thing,” Martinez said. “Having him and Anibal down at the same time is kind of rough, but hopefully we get them back soon.”

Guerra joins Nationals
To replace Hellickson on the roster, Washington activated Guerra, who appeared in 11 games for the Blue Jays this season, all in relief, before being designated for assignment this weekend.

He had just returned home to Toronto and was spending time with his two-year-old son before he got the call he had been picked up by the Nationals. So he made the drive from Toronto to New York to meet the team ahead of Tuesday’s game. Guerra picked up a save and had a 3.86 ERA with 15 strikeouts in 14 innings, and perhaps he could be a boost to this struggling Nationals bullpen.

“Like anything else, I think it’ll all work itself out,” Guerra said about his role in the bullpen. “I think if I go out there and do what I need to do, things happen. But at that point, we’ll just worry about that when it comes up.”

When a player's contract is designated for assignment -- often abbreviated "DFA" -- that player is immediately removed from his club's 40-man roster, and 25-man roster if he was on that as well. Within seven days of the transaction (it was previously 10 days), the player must either be traded, released or placed on irrevocable outright waivers.