Berahino, who is the Baggies' top-scorer this season with eight goals in all competitions, has been involved in a couple of controversies of late.
The 20-year-old was filmed inhaling nitrous oxide from a balloon in a parked car and then slumping down in his seat after West Brom's 3-0 defeat to Manchester United on March 8, with the video subsequently being brought to light last weekend by the Sunday Mirror.
While inhaling the substance - otherwise known as 'laughing gas' - is not illegal, it can pose serious health risks, and Berahino has apologised for his actions.
The England Under-21 international was also part of a bust-up that followed his club's 3-3 draw with Cardiff on March 29, an incident which saw him being hit by team-mate James Morrison.
And, speaking at his press conference ahead of Monday's Premier League trip to Manchester City, Mel said of Berahino: "The most important thing for me is that he is a young player. He has a lot to learn and he wants to learn.
"In the future I think he is going to be a really great player both for West Brom and for the English national side.
"He still has time to make errors and it is up to us as coaches to show him the right path.
"I'm trying to be his sporting mentor. I try to give him advice about what he should do on the pitch.
"I try to tell him what he needs to do in order to remain a top-level footballer for a long period of time.
"But personally I respect all of the players and they need to learn to be able to make their own decisions."
The Spaniard added: "I really think that he does have a very bright, promising future and he can go on to be a great player.
"But what he needs to understand is that no-one achieves anything without making sacrifices.
"I think that of course football has some good things and bad things.
"Players become very popular at a young age and they end up being constantly in the newspapers and on the television.
"Saido is one of these young players and he can go on to be a great player.
"It is part of the head coach's responsibility (to ensure) that he goes on to do this."