The Washington Nationals called up top prospect Anthony Rendon and put the struggling Danny Espinosa on the disabled list amid a flurry of roster moves on Tuesday as they prepared to open a six-game home stand as a sub-.500 team.

The Nationals also designated relievers Henry Rodriguez and Zach Duke for assignment, selecting left-hander Ian Krol’s contract from Double-A to shore up the bullpen. Finally, Jayson Werth came off the disabled list, the first time he’s been available to play since May 2 when he was first sidelined with a right hamstring strain.

Rendon, who turns 23 Thursday, impressed in spring training and his debut stint with the Nationals earlier this season while Ryan Zimmerman was on the disabled list. The Nationals promoted him to Triple-A Syracuse over the weekend after he hit .319 with 11 doubles and six homers in 33 games at Double-A Harrisburg.

A natural third baseman, all three of Rendon’s games at Syracuse had been at second base. Steve Lombardozzi was set to start at second Tuesday night, with Rendon on the bench.

Espinosa has been dealing with injuries throughout the season and his play has suffered. He was hitting .158 and his .465 OPS was the second-worst of any major league player with at least 100 plate appearances.

Krol, the Oakland A’s 2010 Minor League Pitcher of the Year, was the player to be named in the Michael Morse trade. However, the Nationals had said since the trade was made that they were confident they were getting a quality prospect in that deal and Krol, who was switched to a reliever this season, has had great success at Double-A.

In 26 innings of work in Double-A, Krol has a 0.69 ERA. He’s faced 101 batters and has an impressive 0.808 WHIP (Walks plus Hits per Innings Pitched), and the Nationals have been pleased by his progress all season.