Keane is included in the Villa squad after signing on loan from Los Angeles Galaxy until the end of February.
McLeish is refusing to reveal whether the Republic of Ireland international will start but has no doubt he will have a positive influence at Villa.
He said: "In terms of the impact Robbie will have, he will have a great effect.
"His experience and knowledge in the dressing room should be worth its weight in gold. "In my playing career, bringing players into a club of that ilk was a case of not only looking for individuals to do well but looking for others to be inspired.
"Hopefully Robbie can push others to play their best football and I also think there's no bigger threat than someone coming in to take your place.
"I am sure the fans will enjoy seeing Robbie in a Villa jersey. We will just have to wait and see when that is.
"Robbie could make his debut but I am not going to reveal my starting line-up at the moment." McLeish will hope Keane can help Villa put an end to a run of four successive home defeats if he is involved against the Toffees.
He said: "Desperate is a word I don't like to use but the home form certainly is something we want to put right. "We have lost to three of the elite clubs and Swansea beat us after we got a great result at Chelsea which was a real kick in the backside.
"It's up to us. I do feel we have been punished for every little mistake at home. But the one thing we have to concentrate on is concentration.
"I feel sometimes we can have little lapses and two against Swansea cost us two goals.
We have to concentrate from start to finish as we did against Stoke, Arsenal and Chelsea."
Goalkeeper Shay Given is available after a six-week lay-off with a hamstring problem but defender Carlos Cuellar (thigh) and midfielder Chris Herd (ankle) are still ruled out.
Some advice from Manchester United team-mate and former Toffees striker Wayne Rooney helped convince new Everton midfielder Darron Gibson to move to Goodison Park.
Frustration at not getting first-team chances at Old Trafford played a significant part but the 24-year-old said after speaking to the England international - and then Everton duo Phil Neville and Tim Cahill - his mind was made up.
"I was speaking to Wayne about it a bit and after that and coming to see the facilities it was an easy decision," Gibson, who is in the squad to face Aston Villa, told local radio reporters. "He told me it was a great club and he really enjoyed his time and the people here.
"Having a word with him and people like Tim Cahill and Phil Neville convinced me to come."
Gibson has signed a four-and-a-half-year contract for a reported fee of £1million, rising to £2million on appearances. He made 60 appearances in six years at United but knew he had little future at Old Trafford when Sir Alex Ferguson decided to bring Paul Scholes out of retirement.
The 37-year-old, who quit the game last season, was brought back on a short-term deal to provide cover for an injury-stricken midfield and came off the bench in last weekend's 3-2 FA Cup third round victory at Manchester City.
"I was very frustrated [at Manchester United]. It was hard for me at times," the Republic of Ireland international added.
"I think when I did get a chance I did well and obviously I was getting left out afterwards and I was playing one or two games here and there.
"When Scholesy came back the manager told me I was free to go. "Everton had shown some interest a month before hand and the gaffer (David Moyes) wanted me in so it went from there.
"It was very frustrating but I think it was the right time for me to move on and I'm looking forward to my time here.
"I'm really looking forward to kicking on now." Sylvain Distin (hamstring) and Phil Jagielka (knee) are still sidelined so Shane Duffy, who only made his first league appearance as a substitute in the midweek defeat at Tottenham, could start.
Aston Villa V Everton - view commentary, squad, and statictics of the game live.