The Frenchman suffered from Covid-19 following the home defeat to Chelsea at the end of November, then had to deal with the after-effects, meaning he only resumed light training earlier this month.
He was then able to progress to full training this week and, having been assessed by the club's medical department over the last few weeks, Steve Bruce will include him in his travelling party for the visit to Vila Park (kick-off 8pm GMT).
"The good news for everybody is Saint-Maximin's in the squad," United's head coach revealed on Friday. "He's come through all week, trained well, looks in decent shape - which is important - and there's no doubt at this particular moment in time that'll give everybody a huge lift because we know how important he is, especially in a forward area.
"We look to have a bit of creativity so it's good that he's back. We've still got one or two problems in the centre of defence, especially with Fede (Fernández), and Ciaran Clark. Fab Schär, we hope, will make it. We're a little bit light in that area, but I think the good news for all Newcastle fans is that Allan will take some part.
"When you're in the bottom half - or even in the top half - of the league, how important is one player? Certainly Allan over the last 18 months has given everybody a lift. We've certainly missed him. To be out for two months with this horrible virus has been tough, but then again, we've had a few affected by it as well. It looks as if he's on the mend - let's hope he stays well.
"A team like ours is going to miss arguably its most creative player. He's the one that gives us a lot of flair, the one that the system was built around. On a counter-attack, you need a bit of pace up the top end of the pitch, and he gives you it. We've certainly missed him, of course, for his creativity, so it's good to see him back."
Saint-Maximin lit up the league last term - particularly in the second half of the campaign - and while he had yet to hit top form on a sustained basis this season before he fell ill, his performance in October's victory over Burnley, where he scored one and laid on another, was a reminder of what he is capable of.
And Bruce added: "Arguably your most creative player, your player of the year - of course you're going to miss him, and we have missed him for the best part of a couple of months. When he was in and around the team, we looked a threat, we could play that bit deeper and play teams on the counter-attack.
"If you are a mainly counter-attacking team, you have to have pace on the turnover and without Allan we haven't got that blistering pace that he possesses. We're delighted to see him back, he will certainly make us a little bit more entertaining, he will certainly help us win a few games, so it's good to see him in and around it again.
"We have monitored everything that we can this week to see where he is in his fitness; it's fair to say his fitness levels are very, very good, which is good news. Of course, we've got to get the balance right - I wouldn't expect him to be starting on Saturday but he'll be among the squad and there if he's needed."
Bruce - who managed Aston Villa between 2016 and 2018 - is looking to steer Newcastle to a first Premier League victory of 2021 on Saturday. United slipped to a third straight league loss on Monday night, but Bruce insisted: "I thought we had an improvement against Arsenal in the first half.
"We got caught in the second, just after half time, which is getting that balance right of committing too many forward, but it's the way we're trying to go.
"When you're up against it, you need a result and we know this group of players are capable of getting a result - that's for sure. We'll look forward to the challenge of it."
