Chicharito has struggled to hit the ground running at the London Stadium, scoring three goals in his first 10 games of the season but only one since August 19.
“If you're looking for a centre-forward with a history of scoring goals, it doesn't get any better than Javier," Phelan told Sky Sports.
“But there is another side to it: Can you provide the service for him to score the goals? If the service is there for Chicha in and around the 18-yard box, you can guarantee he's one of those players who will hit the target more often than not, which means he'll score more goals than he'll miss.
“It's just a question of how you play to him."