Charlie Austin is in contention for an immediate Saints debut after proving his fitness to manager Ronald Koeman.
The 26-year-old striker arrived at Saints recovering from a hamstring injury.
Koeman admitted he did not expect Austin to be able to train instantly with his new teammates and be ready to play, and so has been pleasantly surprised.
Indeed, such is Austin’s level that Koeman admitted tests have shown he is one of the fittest players in the club, and he therefore could be handed a debut as Saints take on Manchester United at Old Trafford on Saturday.
Koeman said: “It’s possible because if you are part of the squad you have opportunities to play or come in.
“I was of course a little bit worried because Charlie had a hamstring injury before we sign him.
“He had all the medical tests and he did all the training sessions of this week and is really fit, comparing to the rest of the team he’s really fit.
“That’s good news because then he can be part of the squad for this weekend.”
Koeman admitted Saints are suffering from a number of minor injury problems, with Graziano Pelle only touch and go to be for the weekend.
“He is still struggling with his knee the problem he had the last few months,” said Koeman.
“We do some treatment and sometimes he is doing sessions with the rest of the team and sometimes separate of the team.
“If he is in the training sessions tomorrow he is fit enough to be fit enough for the squad for Saturday.”