The Portuguese's absence from the Reserves' midweek victory over Manchester City prompted a series of reports questioning his impact at United, but Sir Alex insists there are only issues with the player's fitness, not his ability.
"Bebe is in a programme of doing endurance work, because his fitness levels aren’t near the levels we’re at," the manager said. "Other than that he’s done well.
"He’s had a couple of attacks - I thought they were pretty vicious attacks - on why he wasn’t playing in the Reserve game. He was never going to be playing in the Reserve game on Tuesday.
"I think those attacks came from a bit of vengeance from two journalists who are banned from here. They saw an opportunity to have a go at the club and I think it’s disgusting. The boy didn’t deserve that. He’s a young boy trying to make his way in football, they didn’t need to do that. I think it was a real bitter attack.
"Ability-wise, he’s excellent. Terrific finisher, we’ve been very impressed with that, and it’s just the fitness levels he needs to get to, as opposed to our fitness levels."
Sir Alex is comfortable to take his time with the versatile forward, who has enjoyed a meteroric rise to prominence since joining United, and insists there is no reason to hasten his playing involvement.
"We’ve not done any serious work," said the manager. "We did some tests on him and there were one or two areas we need to work at, in terms of his