Tony Pulis believes West Brom have been missing the real Saido Berahino for six months.
The striker could face Tottenham on Saturday for the first time since threatening to go on strike in the summer after Spurs had four bids rejected.
He has been benched for the last three Barclays Premier League games after a dip in form and has netted just three times this season.
The Baggies rejected two offers from Spurs on deadline day - the last rising to £23million with several clauses - after he scored 20 goals last season and, ahead of their Hawthorns visit, Pulis is still waiting for Berahino to regain his form.
He said: "If you look at last season the most influential player at the club was Saido. He got the goals which got us the points which kept us in the league. This year we haven't had that.
"For six months we've played with Saido being nowhere near as good as he was last year. It was disappointing in lots of ways. I'm not blaming Saido, not anyone, it's just fact.
"There's no question Saido was disappointed the deal never went through. There are people in the game who can handle it, there are people who can't.
"He's an outstanding player and talent but we haven't had that at the same level as we did last year.
"I'm not saying we can't get him back but we haven't got him back to the same level.
"The problem is the window is coming around again and they'll be all the speculation."
Berahino was also dropped for three games earlier in the season as Pulis felt he was not in the right frame of mind to cope with the spotlight.
Spurs have again been linked with a move for the 22-year-old next month but Pulis insisted Berahino is better off at the Baggies.
"He has to get as fit as he was last year and wash everything else away. He has been given a God-given talent but in the last six months he has not fulfilled the potential," he said.
"He needs to get back to that for his own sake. The best place to do it is here.
"I don't want to get into asking prices and whether he is for sale or not. I'm not interested."
Meanwhile, Pulis is without the banned Claudio Yacob against Spurs while Ben Foster continues to be out with a long-term knee injury.
Pulis insisted there had been no bids for Berahino, although the club have conceded they are powerless to stop interest, and the 57-year-old wants to work with Berahino for as long as possible.
"No one has rung me up and said there is a deal there to be done and no one has rung the chairman up so it's speculation," he said.
"My mindset has always been the same, which is to try to get the best out of the kid while he's here.
"If he's here for the next 10 years and I am lucky enough to be here for the next 10 years then that's what I'll do continuously - try to get the best out of the players.
"My job is to do that and if the chairman decides to sell him then the chairman decides to sell him."
January will be the third transfer window when Berahino has been the focus of speculation at The Hawthorns and while Pulis is confident the forward has learned from past mistakes he knows only the England Under-21 international can get himself back on track.
"I think it takes time. There are different people, different characters," he said.
"We are all different and some people take over things straight away and others take time.
"It's important that he realises and recognises that he has got wonderful talent.
"Irrespective of what we say, the lad has to pick up the baton himself and that's important.
"For all the talk we do, the important thing is that the lad who is running this and can control this has got to pick the baton up and that's what Saido has got to do."