The Senegal international has impressed for the Baggies ever since joining on loan from Galatasaray.
But he will be the first to admit he should have scored more goals with the forward having missed some chances he should have scored whilst also being unlucky with some offside calls.
Diagne, though, did finish off a brilliant team goal during Albion’s thumping 5-2 win at Chelsea last weekend.
That was his second goal in nine outings for the Baggies. And Allardyce hopes he will now catch fire for the remaining eight games of the campaign.
“It was a great relief for him (Diagne) that he scored at Chelsea,” Allardyce said.
“You couldn’t wipe the smile off his face when he put the ball in the net and in the dressing room afterwards.
“Hopefully, that sets him up for better things.
“He could have already had six or seven goals this season quite easily.
“He has been slightly offside. He had two very good chances against Burnley and against Manchester United that he could have easily scored.
“But hopefully the one against Chelsea will get him on a streak of scoring when chances come his way.”
Diagne’s goal at Stamford Bridge was his first in six outings.
Matheus Pereira netted a brace against the Blues having not scored in eight games, while Callum Robinson also found the target twice having not scored since September.
And Allardyce was asked how he has helped his forwards keep their belief during their barren runs.
“Matheus (Pereira) hadn’t scored for a while and Callum (Robinson) came on and got two fantastic goals as well,” the boss continued.
“I think the first thing is providing them with enough service and enough opportunity.
“That was limited in the early part of my time at the club.
“Now that has lifted and been increased dramatically by the training sessions we have done and by trying to give the players a bit more belief.
“And, of course, the new players we brought in in January have helped improve our all-round ability – defensively and attacking wise.
“There is one thing you can’t do as a manager or coach, you can’t teach a player to score a goal.
“You can practice and you can talk about it. But when it comes down to it, it’s not something that is coach-able.
“Believe you me, if anyone tells you they can coach it they are not telling you the truth. I’ve had many a striker coach – Teddy Sheringham, Frank Stapleton – in my time and they talk about what they do and how they did it.
“That is great information. But when you are out on the pitch, you have to get yourself in those positions.
“If those lads keep up that goal-scoring ability, that will give us an opportunity to win the games we need to win – starting with Southampton on Monday.”