The 32-year-old former Wests Tigers second rower broke a bone in his foot in the warm-up to the opening game of the season at his former club Leeds and said he felt he had let the club down, but he is now fully recovered and is excited at the prospect of leading the team out against London Broncos at the KC Stadium.
Gentle said: "He just needs to get out there, dust some cobwebs off and get his timing back. He only came back into training a week and a half ago. There's nothing I expect, he's just got to fulfil his role, play his part and not worry about anyone else's."
He added: "It's very difficult for your captain to be sitting in a losing meeting and not being able to say anything. You feel like an outsider.
"But, as he got closer to playing, his input has been more, he's become more vocal."
Hull, who are in the top eight only on points difference, have received a double boost as they enter the second half of the regular season, with Australian stand-off Daniel Holdsworth also making his comeback from injury against the Broncos.
Signed from Salford in the close season, Holdsworth played in the first three matches of the season but picked up a head injury in the draw at St Helens and complained of headaches over the next month.
Like Ellis, he has been given a clean bill of health and Gentle cannot wait to see his two high-profile signings in harness for the first time.
"You can see by the difference in training what the two of them have brought to us," Gentle said.
"They're not going to win us the game and they're not going to lose us the game but their presence is definitely going to lift us."