Despite Florian Lejeune and Sean Longstaff remaining sidelined for the rest of the season, Benítez has a fully fit squad for United's evening clash against the Saints at St. James' Park.
The Spaniard expects that Lejeune, who suffered a significant knee injury in United's 1-0 defeat against Crystal Palace, can bounce back from an expected lengthy spell on the sidelines after carrying out a successful operation this week.
Benítez said: “I saw Longstaff today – he is walking around and getting stronger. Other than him and Lejeune, the rest of the squad are fine.
“Florian had the operation, and talking with the doctor, he said everything had gone well – as we were expecting. In terms of the timescale, we think that in a couple of months we will see how he’s progressing and how long it will take. In this case, we have to give him time.”
"We sent him to Rome with a specialist which is quite good. He was doing a great job with the other knee and we are sure he will do the same with this one. It depends on the rehabilitation but I think it will be quite quick."
The Magpies sit in 15th place, seven points above the relegation zone, after an important 1-0 away win at Leicester City and would move past the 40-point mark with a victory against the South coast club, who lie two points adrift of United.
However, Benítez felt that there are attacking comparisons with Ralph Hasenhüttl's side and Crystal Palace - who ended United's five-game winning streak on Tyneside - and believes his side must learn from their recent home defeat in order to achieve maximum points.
He added: “I said 38 points (would be enough) a long time ago. Cardiff have won a couple of games before that, and now it’s even more important for us to win another game, be sure everything is fine and then we can start thinking about how high we can go in the table.
“We played a very good game and everyone could see that. Southampton are also coming into this game with a lot of confidence, so I think it will be an interesting game.
“I think it will be very similar to the Palace game, but hopefully the result will be different. Both teams are similar – they are very good on the counter attack, aggressive, and they have pace up front. We know we can’t make the same mistakes.
"Today, I was talking to some players and said we just have to concentrate on what we have to do. We are professionals and have to do our job in the best way possible. I think the players know that.
"Each one is different and have their own ways to approach the situation. We need to make sure we can get three points in the next game and try to go as high as possible in the table.
“It depends on us, first of all, but also Southampton, Brighton and Cardiff. It's very tight but I’m sure if we win this game, then that will be enough. We have to be sure we don’t approach the game with complacency. We have to be really focussed – like they will be.”
