After a second-half to last season to forget, Morata has started to find his goalscoring touch again.
The Spain international has scored four goals in his last four Premier League games for Chelsea.
He bagged a brace in the 3-1 win over Crystal Palace last Saturday but Merson was still not completely satisfied.
Morata missed the chance to score a hat-trick at Stamford Bridge, failing to beat Palace keeper Wayne Hennessey with a chip when through on goal.
And Sky Sports pundit Merson says that showed exactly why Chelsea need to sign a new striker in January.
“They need a forward though, come what January,” Merson said.
“You know what summed it up for me more than anything last Saturday that they need a centre-forward?
“He’s going through one-on-one with the keeper to get his hat-trick.
“(Alan) Shearer, (Michael) Owen, (Robbie) Fowler, (Ian) Wright, (Harry) Kane – they roll the ball down the side (and score).”
Soccer Saturday presenter Jeff Stelling leaped to the defence of Morata’s miss against Palace, saying: “But they’d won the game.”
But Merson says that is not the attitude of a goalscorer.
“They don’t think like that, goalscorers don’t think like that,” he replied.
“Goalscorers go ‘bang, score, get the ball out, sign that for me’.
“He (Morata) was very good, he was very good. But it was a prime example, you’ve got to be a goalscorer.
“He’s going through and just tries to dink the keeper. If this was Shearer going through, he would have just smashed it.
“He’s not doing too shabbily but Chelsea to win the Premier League will need a centre-forward to get 20-25 goals this season.
“Jorginho’s not going to get you goals, (N’Golo) Kante’s probably going to get you three if that for the rest of the season, Pedro might get three or four.
“So you need someone who’s going to get 20 goals at least in a season.”