AFC Bournemouth
The winger, who scored against United last season, is out along with defender Tyrone Mings.
But Howe is delighted with Mings' progress throughout pre-season and revealed that the 23-year-old could return in September.
"Junior Stanislas is definitely out," Howe said.
"There are a couple of niggles but in the main the squad is in good shape.
"I've been really impressed with Tyrone this pre-season. He's been in and around the group and has been positive, he's worked incredibly hard in rehab.
"Tyrone has shown great discipline and I think he's grown for the experience in a positive way.
"We'e seen him, albeit not in full contact training, but I'm excited for the future, I think we could see him in September, maybe late September.
"Hopefully he gets there because he deserves it."
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