Munster’s talisman lock O’Connell has been linked repeatedly with a summer move to Toulon, despite the Top 14 club denying any contact in a statement last week.
O’Connell’s Munster and Ireland contract expires in summer 2016, with the 35-year-old consistently coy on whether he may retire after this autumn’s World Cup.
Toulon’s World Cup-winning locks Bakkies Botha and Ali Williams will retire this summer, leaving Mitchell to admit that the Cote d’Azur club would be fortunate to sign O’Connell as a replacement.
“At this point in time it’s speculation, but we’ve got two guys retiring after fantastic careers, individually,” said Mitchell.
“Having someone again with such experience to add to this group, from worldwide in rugby, his knowledge, the presence he would have on some of our younger players, I think he’d be an invaluable addition to our squad.
“And if it does happen and he turns up in our squad come pre-season then I’m sure the squad would benefit from his presence in the group.”
Toulon are gunning to make history by landing a third consecutive European crown in Saturday’s Champions Cup final, against Clermont at Twickenham.
French Top 14 champions Toulon edged out Leinster 25-20 in a tense semi-final that stretched into extra time.
Wallabies wing Mitchell hopes the poise under pressure that edged Toulon home against Leinster will surface once more against rivals Clermont.
“First and foremost that semi-final highlights just how close this competition is,” said Mitchell.
“It highlights how much set-piece, territory, taking points when they are on offer, how much all these things count at the back-end of the season.
“It doesn’t get much tighter than that match against Leinster.
“We can take confidence from the fact we were able to keep as calm as possible, and focus on what needed to be done in those crucial minutes.
“One thing we’re pretty lucky to have is big-game experience right across the board, people who have got the job done in different competitions across the world throughout their careers.
“So come the 80th, 90th or even 100th minute, we’ve got guys staying calm and worrying about the detail, and how to execute our roles as opposed to getting a bit frantic and lost in the occasion.”
Mitchell seriously considered joining Leinster before settling on Toulon when leaving Australia in 2013.
The 63-cap wing admitted the presence of best friend Matt Giteau tipped the balance in Toulon’s favour on a decision he feels hindsight has helped vindicate.
“I was pretty sure it was time for me to move abroad, I wasn’t the type of player to throw the net far and wide,” said Mitchell.
“I narrowed down a few clubs and it basically came down to Leinster and Toulon, both clubs with very impressive set-ups, squads and strong histories both domestically and in Europe.
“Having the comfort of my best mate Matt Giteau playing here is a big thing, as is the climate here.
“That really suits me: I’m a pretty well-known whinger when it’s cold, so I’m not sure I would have been good for the team environment come winter in Dublin! Being serious though I just felt this was a better suit for me, and that’s how it’s turned out.
“Coming here on my own without a partner or family or anything, having the benefit of Matt (Giteau) and his family here, that’s been a really big bonus for me.”