The 24-year-old, who has scored five times for the Magpies so far this season, missed last weekend's draw at West Ham United and has not trained with his team-mates this week.
But Howe has not given up hope of Saint-Maximin being able to play some part in West London as the Magpies look to build on their current six-game unbeaten run in the top flight.
"He got a bang on the calf against Aston Villa," explained the head coach when asked about Saint-Maximin on Friday. "In terms of his rehab, he's been away to get intensive, specialised treatment abroad. We felt that was the quickest way to get him fit. He's in a very good place mentally and he's very eager to return.
"Not too much has changed with some of the lads that are out - Callum Wilson, Matt Ritchie. Maxi, we're going make a late call on. He's been away getting intensive treatment. We said when he suffered the injury that it wouldn't be long term, so we're keeping our fingers crossed on him.
"And then you've got Ryan Fraser (who) will be okay. He came off the pitch against West Ham but it looks like he'll be fine."
Howe, who revealed that United have had "a bit of illness in the camp this week but nothing too serious," also hopes to have Javier Manquillo available after the Spaniard limped off against Villa with an ankle injury.
"Manqui came through a couple of training sessions this week," he said. "I wouldn't say he's 100 per cent fit but he's certainly getting closer to being fit and available."
Emil Krafth deputised for Manquillo at West Ham while Jacob Murphy came in for Saint-Maximin at the London Stadium.
And Howe added: "It's absolutely vital that every player that steps into the team, even if they haven't played for a period of time, knows their job, knows their role, knows what's expected of them and is physically ready to perform.
"The pleasing thing from last week is we had a few players that did that. I think that's testament to their attitude and professionalism. I've said all along the group here is very, very good in that respect - always prepared to help the team ahead of their own wants and needs, especially with the position that we're currently in, so long may that continue."
Brentford were Newcastle's opponents in Howe's first game in charge of the Magpies back in November - albeit the head coach had to watch from a hotel room rather than being in the dugout after testing positive for Covid-19 on the eve of the match.
The Bees enjoyed a superb start to their first season in the Premier League but have found victories harder to come by in recent weeks, although Howe feels that injuries have contributed to that.
"They've obviously had a couple of players missing," he said. "I think (David) Raya was a big miss for them earlier in the season and now Ivan Toney's been out for a few games. They're big players.
"But Thomas Frank has done a brilliant job. Last season getting promoted and the manner that they've played this season, I think they've been been very good and we don't underestimate them, especially at home.
"We've got to be prepared for a tough encounter - but we need to maintain our standards from our recent games."
