Saints have kept close tabs on former Man City youth captain Charles, 21, during his impressive loan spell with Sheffield Wednesday in the Championship.
The Northern Ireland midfielder has said he is open to staying with the Owls until the end of the season but Martin revealed Saints will assess and decide if they want him back.
Chelsea's Ugochukwu, 20, is unavailable for Wednesday's home game against his parent club having not made the squad for Friday's trip to Brighton.
Saints have been linked to activity in the January transfer window but can only free up a Premier League loan spot by offloading Ugochukwu or Maxwel Cornet.
Martin told the Daily Echo: "I think if it's not Chelsea, he's probably back in the squad. He wasn't in the squad against Brighton and he knows the reason why.
Lesley Ugochukwu is at Saints on a season-long loan from ChelseaLesley Ugochukwu is at Saints on a season-long loan from Chelsea (Image: PA) "Every game is different so it doesn't mean he's not going to be in the squad moving forward. We will assess the situation and just have to assess it game to game."
He added: "I think Shea went on loan to do exactly what he's done, to play every single week, rather than to be a squad player here.
"It was his first full season last year, we wanted him to build on that. We're really pleased with his development. It's gone exactly how we wanted it to, for him and for us.
"It's gone really well and it continues to go really well. We have another month to assess things. We have an option to recall Shea if we choose to.
"But we're not going to call him back unless he's going to come back in and play and impact the squad and be a big player for us.
Shea Charles was voted #SWFC’s Player of the Month for October. 👏🦉#SaintsFC pic.twitter.com/S5LcWxH9zT
— Just Saints (@JustSaints_) November 1, 2024
"He needs to keep doing what he's doing. We'll continue to assess our situation and what we need but he's never not been in our plans. Same with Sam Edozie.
"We really believe that he will be a big player for us, otherwise we wouldn't have invested so much money in him. He had a really good first season.
"He played a lot of games and impacted a lot of games for us. In his first season as a professional player, he was part of a promotion-winning team.
"It's been great for him this season in terms of minutes played. We will assess it. We're in constant contact with him and we'll see what January brings."
Ugochukwu's last Premier League start came in the 3-1 defeat at AFC Bournemouth in September and he has made three substitute appearances since.
Charles, whose deal to bring him to St Mary's could be worth up to £15million, has started every match in the Championship for Sheffield Wednesday this season.