Blow for Manchester United as Nemanja Vidic faces five weeks on the sidelines

Central defender Vidic limped out of the 2-1 win at West Bromwich Albion last Sunday, although it was initially anticipated a nerve issue would keep him out for just two weeks.

However, Ferguson yesterday said: "The situation has reversed and Vidic has a calf muscle injury, which means he'll maybe be four to five weeks."

There was some good news for the Old Trafford manager, though, with Vidic's regular defensive partner Rio Ferdinand seemingly set to return more quickly than anticipated from a hamstring injury also sustained at The Hawthorns.

Ferguson's assessment at the time was Ferdinand would be sidelined for six weeks, missing England's Euro 2012 double-header against Bulgaria and Wales next month, as well as the start of United's latest Champions League quest.

However, following a visit to a specialist in Munich during the week, the injury is not as bad as first feared.

Although the centre-back has not been definitively ruled out of Monday's clash with Spurs at Old Trafford, it is more likely he will be ready to face Arsenal at home six days later.

"Rio is not as bad as we thought and he could be ready for our game with Arsenal," said Ferguson. "I don't think he'll be ready for Monday, but it's amazing how assessments can change in the space of a few days."

Ferguson will now pair Phil Jones and Jonny Evans together at the heart of his defence for the visit of Spurs, whilst Chris Smalling will fill in at right-back.

Ferguson at least has Patrice Evra available again at left-back after he missed the game at West Brom with a knee injury. Darren Fletcher (virus), Javier Hernandez (concussion) and Antonio Valencia (ankle) are all closing in on a return, but are not yet ready, whilst Michael Owen is still out with a back problem.

With the likes of Gary Neville and Paul Scholes now retired, youth is again at the forefront for United as Ferguson masterminds the latest rejuvenation of his squad.

It was Alan Hansen who once famously remarked of Ferguson's 1995/96 side that "you never win anything with kids", only for United to claim the double that year. The team beaten 3-1 by Aston Villa on the opening day 16 years ago that prompted Hansen's quote was, on average, a year older than the one that finished Sunday's season-opening victory at West Brom.

"We were always aware we had players who were coming to the end of their careers.That has been on the horizon for us for quite a few years," said Ferguson, who is relishing watching his latest crop of young guns blaze a new trail at Old Trafford.

"We knew it was going to happen, you don't want it to, but it does and there's nothing you can do about it. Age catches up with us all. So we've replaced the players who have left us, and we've still players at the club in their 30s, which is a lot of experience.

"At some point when the young players may hit a pocket there will be enough experience to augment the challenge we're after this year. It is a very young team at the moment, but it's one full of energy and of great ability, and I'm enjoying watching them."

It is likely there will be only one player over 30 in the starting line-up for Monday's visit of Spurs: Evra. Aside from Evra, ahead of 20-year-old goalkeeper David De Gea, Jones and Evans, 19 and 23 respectively, line up at the heart of the defence, with 21-year-old Smalling in at right-back.

"I'm not worried about the young players filling in at the back," said Ferguson. "Evans has ample experience, of course, and has been at the club since he was 12. He's played plenty of first-team games.

"Jones has the experience of playing for Blackburn last season in the Barclays Premier League. I thought he and Smalling were the stars for the England Under-21s in the summer, and Chris had a fantastic first season with us, and he's continued his progress this year.

"So I have absolutely no issues whatsoever with playing those guys."