WASHINGTON -- Before opening their four-game series vs. the Nationals on Thursday, the Marlins did some roster shuffling.
Martin Prado was reinstated from the disabled list and was in the starting lineup at third base for the first time since May 25. Hard-throwing reliever Tayron Guerrero was placed on the 10-day disabled list with a left lumbar strain, and rookie right-hander Ben Meyer was recalled from Triple-A New Orleans.
The club also designated backup outfielder JB Shuck for assignment. Shuck had been used mostly as a defensive replacement and an occasional starter against right-handed pitchers.
"[Prado] feels ready to go," Marlins manager Don Mattingly said. "We're confident. Here we are. In general, we'll be able to use him now to give other guys periodic days off. Put a little plan in place, so he's not playing seven or eight days in a row."
The series of moves gets the 25-man roster back to 13 pitchers and 12 position players. In Wednesday's 3-0 win over the Rays at Marlins Park, Miami had 12 pitchers and 13 position players.
Guerrero has been a staple in the back end of the bullpen, compiling a 1-2 record and a 4.28 ERA in 40 innings, with 54 strikeouts and 24 walks. One of the hardest throwers in the game, the 6-foot-8 right-hander has a four-seam fastball average of 98.4 mph, which is third highest among all pitchers with a minimum of 100 fastballs thrown, according to Statcast™.

Only Jordan Hicks of the Cardinals (100.3 mph) and Yankees closer Albertin Chapman (99.3 mph) have a higher average fastball velocity than Guerrero.
"That's been going on, probably 10 days, two weeks. [Guerrero]'s been kind of fighting through it," Mattingly said. "The usage of it, he's been kind of every other day, not back to back at all. With the situation of the pitching, we felt like we really couldn't protect him anymore. We just made the decision to [rest the ailment], and get this thing under control."
Guerrero's DL stint is retroactive to Wednesday. The right-hander threw an inning on Tuesday in Miami's 16-inning, 9-6 loss to Tampa Bay. In that outing, his velocity wasn't an issue, as he threw a maximum fastball velocity of 101.3 mph, and his fastball average was 99.1 mph. The slowest pitch he threw was 97.1 mph.
Prado's return gives the Marlins' offense a veteran presence and allows the club to rest some of its other regulars. On Thursday, second baseman Starlin Castro was given a breather, as Miguel Rojas played second base.
Even with Prado back, the organization will be looking for ways to manage his usage. Thursday was just the 62nd game he's played in the past two seasons.
Prado has been hindered by left hamstring injuries the past two seasons. The 34-year-old old opened the season on the DL due to a hamstring injury, and Thursday was just his 25th game of the season. He is batting .194 in 93 at-bats, but he's a .290 career hitter with 97 home runs.
Prado said he aims to take extra measures in his preparation to make sure he is ready to play when called upon. One area is his postgame weight training.
"I'm not 20 or 25 anymore," he said. "I think when you get to a certain age, you have to back off a little bit. In my mind, I've never had that medium or low workout stuff. I've always been pushing the envelope all the way, 100 percent. Sometimes, it can be your worst enemy."
Meyer, who was called up for the third time, is a long reliever and spot starter option.
Worth noting
• Shortstop JT Riddle was scratched from the starting lineup on Thursday, and with the Nationals going with left-hander Giovany Gonzalez on Friday, there's a good chance Riddle is held out a second straight game. Riddle is dealing with left hip soreness, which he sustained on his head-first dive at home plate Wednesday.

"Being cautionary about it," Riddle said. "I woke up this morning, it just didn't feel the best."
• By designating Shuck, the Marlins' only true center fielder is Cameron Maybin. Mattingly said utility infielder Yadiel Rivera, who started for Riddle at shortstop on Thursday, will see time in center.
When a player's contract is designated for assignment -- often abbreviated "DFA" -- that player is immediately removed from his club's 40-man roster. Within seven days of the transaction (had been 10 days under the 2012-16 Collective Bargaining Agreement), the player can either be traded or placed on irrevocable outright waivers.