The Tigers scrum-half suffered a knee injury during his team's 26-14 Guinness Premiership semi-final victory over Bristol at Welford Road.
And the clock is ticking on his availability for next Saturday's Twickenham final against Gloucester, plus Leicester's Heineken Cup final appointment with fellow English heavyweights Wasps at the same venue eight days later.
Assessing injuries sustained by Ellis and wing Tom Varndell, Tigers head coach Pat Howard said: "I have done a lot of rotation in the Premiership all year, and if someone has to step in, then he has probably played 10 or 12 games.
"If that happens to be a Premiership final, then fantastic for him. It's a great showpiece for him to stand up in."
With the EDF Energy Cup already collected, Leicester are now two wins away from achieving a mighty clean sweep in Howard's farewell season before he returns home to Australia.
He added: "We know we've got two very hard teams to play, and that we will have to play them back to back.
"We've also had a lot of hard games on the trot. A lot of blokes came off the back of the Six Nations, so it has been an intense period and the players deserve an immense amount of credit and respect."
Gloucester, meanwhile, eased into their first Premiership final since 2003 when, after topping the table by a 15-point margin, they were stung 39-3 by Wasps at Twickenham.
Head coach Dean Ryan said: "Parallels will obviously be drawn with what happened in 2003, but this team won't carry that burden.
"If we carried history around with us, then we would be burdened, but we don't."
And Gloucester scrum-half Peter Richards, one of his team's try-scorers in a 50-9 Kingsholm rout of Saracens, added: "We are hitting our straps at the right time.
"It is about coming into your best form at the end of the season so you have the best chance of winning the play-off semi-final and final.
"On our day when our team clicks, I would have thought we are the most attacking, dangerous team in the league. There are a lot of attacking threats.
"At the end of the first half Saracens were dead on their feet, but we were full of beans, and we managed to run them ragged.
"Our ambition to reach the final was so apparent during the game. When we get to Twickenham, either team can win, but it is about who has got the bottle and the discipline on the day."
Richards also praised South Africa-bound England tourist Hazell, who delivered another stunning performance in the number seven shirt.
It is two seasons since 29-year-od Hazell won the last of his six caps, and Richards revealed: "It has been a mystery to most of us in this part of the woods why he has not been involved with England for the last couple of years."