The pair have been in excellent goalscoring form of late alongside top scorer Robin van Persie.
Van Persie has found the net 11 times already, while Chicharito and Rooney are on six and three respectively.
All three front men netted in the 3-1 win over Braga on Wednesday night and Sir Alex fully expects plenty more goals to follow from the trio.
"It's a healthy combination we've got," said the boss. "Robin has come to us at the right time, no doubt about that. He's got us 11 goals so far.
"I don't think it's a problem relying on Robin. Last year, we lost on goal difference and I don't expect us to lose on goal difference again. I think Robin may make that difference.
"The way young Chicha has started this season, I'm certain he'll get to 20 goals plus. He's on six and he's getting back to where he was a couple of years back. The summer's rest has helped him enormously and he's looking fresh and aggressive in his running. The boy is always a handful.
"Wazza will get there too, he'll get 20 goals plus I'm sure."