Former Leeds and Leicester ace Gradel suffered a serious knee injury that ruled him out for six months of last season, before he returned to help save the Cherries from relegation.
But the Ivory Coast winger relapsed over the summer and has since lost his place in Howe's side.
Even so, the Cherries boss believes Gradel could still be the final piece to his team once fully fit, saying: “He could be a huge player for us if we can get him back to his very best.
“When he came back into the team at the back end of last season, he was very good.
“Naturally, he had that period where the adrenaline rush had gone and he had to find his form and fitness again.
“And he's in that moment now where he is coming back to his very best levels.
“It's very hard to come back after nearly a year out and be firing and then maintain that. I'd say it's almost impossible.