Murphy looks set to play his last game for the club in Wednesday's Clydesdale Bank Premier League clash at Celtic Park after holding talks with npower League One promotion hopefuls Sheffield United.
Murphy rejected a move to Blackpool on the final day of last January's transfer window in order to help Motherwell seal a slot in the Champions League qualifiers but his salute to the Fir Park fans following Saturday's 2-2 draw with Kilmarnock looked like a farewell.
Manager Stuart McCall expects the 23-year-old to move on after the Celtic Park clash and Humphrey feels his team-mate will go on to bigger things.
The Jamaica international said: "I'm sure it will be emotional for him and I'm sure it was emotional for his last home game. But he will be looking forward to it and will want to leave on a high.
"He has been terrific for the four years that I have been here. I think it's a long time overdue. He has done terrifically well and I wish him all the best.
"Obviously we will see him for the game on Wednesday but he deserves everything he gets because he has been fantastic."
Murphy has scored nine goals in his last 13 games from midfield and Humphrey believes his friend can improve further.
"I think he can be unbelievable," the former Shrewsbury winger said. "He has always had the right head on him to do well and I think he can go on to big things."
Murphy has a difficult game to make a farewell impression with Motherwell having scored just three times in their last 12 visits to Celtic Park, although that meagre return has yielded four points and they sit just six points behind Celtic.
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