"With it being a lefty, kind of give him a day to take a mental break and tomorrow being an off-day and get ready to go," Porter said. "Like I told him, you have an off-day until the game is hanging in the balance, so be ready."
Meanwhile, Robbie Grossman returned to the lineup Sunday after sitting out the first three games of the series. Grossman was in an 0-for-17 drought and had not played since going 0-for-3 with a walk and a run scored on Wednesday in Washington.
"He's worked extremely hard in the cage with some early hitting with [hitting coaches] John Mallee and Ralph Dickenson," Porter said. "He's watched a lot of video from this year and last year, and I felt like he needed to kind of take a step away and hopefully we can get the Robbie Grossman back that we had the second half of last year."
Grossman and Singleton were not the only Astros players who began Sunday in funks at the plate. Chris Carter (0-for-19), Matt Dominguez (0-for-12) and Dexter Fowler (0-for-12) were also struggling. Fowler homered on the first pitch Sunday.
"What you hope is the time away clears your mind of a lot of the negatives that could take place when you're not swinging the bat well and that they're able to get back into the batter's box and get back on the field with a clear mind," Porter said.
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.