Howard avoided becoming the first Phillies non-pitcher to go hitless in 36 at-bats since Desi Relaford in 1998. Len Matuszek also went hitless in 36 at-bats in 1982-83, with no non-pitcher going longer than 37 at-bats without a hit since '74.
Phillies right-hander Brett Myers went 0-for-40 from 2006-08.
"[Ibanez], pretty good hitter, so it happens to the best of them," Mackanin said. "It was nice to see Howie break out, so that probably took a little pressure off. You know how hot he can get. We're just hoping he can get hot again."
Mackanin has told Howard he will not start against left-handed starters the rest of the season, although he also said he would not pinch-hit for the veteran first baseman when a left-handed reliever entered the game to face him.
Howard had been one of the most feared sluggers in baseball for years, but he has posted a .426 OPS against left-handers this season, which would be the lowest mark in baseball if he had enough plate appearances to quality. Howard also has a .620 OPS against lefties since 2011, which is 233rd out of 252 hitters in baseball in that span.
Howard left the clubhouse before it opened to reporters, so he was unavailable to comment.
"I've seen him in slumps before," Mackanin said. "In the past, he's been very streaky. I haven't seen him in this big of a slump. There's no other alternative. He's got to keep playing and he's got to keep swinging the bat."
Howard is making $25 million this season. He will make $25 million next season, plus he will receive a $10 million buyout on a 2017 club option. The Phillies have tried to trade him for more than a year, but have found no takers -- even after offering to pay almost everything owed on Howard's contract.
So Howard will continue to play this season. He could be back next season, too.
"He's our first baseman," Mackanin said.
Todd Zolecki is a reporter for MLB.com. Read his Phillies blog The Zo Zone, follow him on Twitter and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.