Conor O'Shea has told Joe Marler to keep playing "on the edge" despite the England prop seeing a sports psychologist to keep a lid on his temper.
Harlequins boss O'Shea believes Marler can actually benefit in the long-term from a wretched few months where he was banned for abusing Wales prop Samson Lee, then for kicking Grenoble hooker Arnaud Heguy in the head.
Marler will return from his two-week ban for kicking Heguy in Friday's European Challenge Cup final clash with Montpellier in Lyon, with boss O'Shea backing the 25-year-old to master his demons.
"We want to see him on the edge because that's when he's at his best," said O'Shea.
"We want him to be physical. Joe learns lessons like we all do.
"People learn lessons - some aren't great, some are life lessons but these guys do it in the glare of publicity.
"They're not perfect but they make their mistakes to millions.
"Joe's had a pretty tough couple of weeks but I look at him as a 25-year-old loose-head prop who could become anything over the next couple of years.
"His sheer physical presence on the pitch for us is massive: Joe Marler to me is the best loosehead prop in European rugby."
O'Shea will take charge of Harlequins one last time in Friday's Challenge Cup final, before becoming Italy's head coach this summer.
The former Ireland full-back has backed Marler to thrive now he has engaged the help of ex-England cricketer turned sports psychologist Jeremy Snape.
Marler had only just returned from his ban for calling Wales prop Lee "Gypsy boy", when he kicked out at Grenoble's Heguy.
O'Shea believes the "very articulate" Marler is now realising he cannot afford to be so "obtuse" in certain aspects of his working life.
"Joe wants to control things, and he will benefit hugely from it," said O'Shea.
"He's posed me some of the funniest and some of the biggest problems in my time: he is different, but he is very, very bright.
"It has been an interesting challenge. I didn't appoint him captain here for nothing, I didn't appoint him captain when he was a 17-year-old for an England Under-18s team for nothing.
"He is very articulate when he wants to be and he is followed massively by people within a group, but he has other areas that he has to work on.
"I find him incredibly engaging company but I know there's the obtuse side of Joe, which is probably the side the media have seen a lot.
"Maybe these last few weeks will help him in the long term."
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