The Brazilian was outstanding in the 5-4 Capital One Cup defeat against Chelsea, assisting all three of United's goals in his time on the pitch, and is giving the manager plenty of encouragement.
"Ando was the best player on the pitch [on Wednesday] until he tired," said Sir Alex. "He needs games now and hopefully we can give him them."
The Reds have no additional injuries coming out of the two action-packed clashes with Chelsea.
"Chris Smalling is training with the first-team squad on the football side which is good news," stated the boss. "He's not ready for us yet but it's still encouraging. We've got options. Chicharito is in terrific form. He is improving all the time. The key to Chicha's form is the decent rest he's had in the summer.
"Every game against Arsenal is always a big one," he added. "It won't be any different tomorrow.
"They have proved defensively this year that they're a stronger, more physical team. I watched them last week against QPR and it'll be a hard game."