"We saw what he's capable of doing at the end of last year," Luhnow said. "He's capable of being a very effective two-way player and we handed him that left-field everyday job and he played every game so far this year.
"He was given every opportunity. It was disappointing for him primarily, but also to us. I'm fully confident that Robbie will go to Triple-A and find his stroke and sort everything out and make it back here later this year and will help us win ballgames. I'm confident of that."
Grossman had two stints with the Astros last year in his Major League debut, hitting .322 with a .816 on-base percentage in his final 35 games after getting recalled in July. He hit just .198 in 28 games early in the year, but made some adjustments in the Minors that paid off. He'll have to do that again to get to back to Houston.
"I told Robbie, 'Look, we've been here before,'" manager Bo Porter said. "'You arrived last year and you struggled. You went back and you went down and took care of business and you came back and had a productive regular season.' I said, 'Treat this here the same. Go down there and take care of business and you'll be back here in short order.'"
His departure frees up some playing time for L.J. Hoes in left field, especially now that George Springer appears destined to start in right for the foreseeable future. Hoes played left field in the Minor Leagues with the Orioles and when he made his Major League debut.
"It's tough sitting over here feeling you can help the team and seeing those guy struggle," Hoes said of the Astros' early-season offensive woes. "You have to understand, it's what they want to do. It's a process and you have to have confidence in your teammates and their ability to snap out of it. Robbie's one of my good friends, and [Alex] Presley has been my teammate, and I've been talking to them to encourage them and telling them it's early in the season and to keep working and to break out of it."
Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.