Sir Alex Ferguson often describes Manchester United as “a bus that waits for no man” and, having told his players what he thought of their miserable final performance of 2007, several of them return to action against Birmingham City today with a point to prove.

After being subjected to a fearsome blast of the so-called “hairdryer” in the dressing-room at Upton Park on Saturday evening, Wes Brown, Louis Saha and others were left in no doubt that they are in danger of being left behind as United look to drive forward again in 2008.

Ferguson is a reluctant mover in the January sales, often claiming that there is little value to be had, but the potential availability of Dimitar Berbatov, the Tottenham Hotspur forward, has not gone unnoticed and nor has the prospect of signing either of his two top full back choices, Philipp Lahm, of Bayern Munich, or José Bosingwa, of FC Porto.

The prospects of signing any of these players this month remain distant, with the likelihood that United will wait until the summer, but in the cases of Brown and Saha, time is running out if they are to secure their places in Ferguson’s long-term plans.

Saha will reflect on 2007 as an annus horribilis, having scored only four goals in the Barclays Premier League and severely tested Ferguson’s patience with his slow recovery from a series of injuries. The manager has been willing to indulge Saha, who scored twice in the 4-0 victory away to Sunderland on Boxing Day, but several below-par performances have raised doubts about his future at Old Trafford, which will look even bleaker if Ferguson succeeds in his bid to sign Berbatov, whether this month or, more probably, in the summer.

Brown’s situation is more clear-cut, with the defender in the final six months of his contract and Ferguson insisting that the club will not meet his request for a deal in the region of £55,000 a week. Brown has been a regular in the United defence this season, starting all but one of their 20 Premier League matches in Gary Neville’s absence through injury, but Ferguson is adamant that United will not improve on what he says is their final offer.

United may be tempted to sell Brown to Newcastle United or Tottenham for £5 million now, rather than allow him to leave on a free transfer in the summer, but the 28-year-old is determined to stay until the end of the season, having not yet abandoned hope of agreeing a deal.

Brown would appear integral to United’s hopes this season, but with Danny Simpson and Gerard Piqué showing signs of promise and Rafael and Fabio Silva, the teenage Brazilian twins, due to arrive from Fluminese this month, Ferguson believes that the club are well covered in defence. He is also optimistic about the fitness of Neville, who has suffered a series of setbacks since injuring an ankle in March. “We’re happy with Gary’s progress and we’re assured he’s OK now,” Ferguson said. “It’s just a matter of getting him games.”

Park Ji-Sung, who has been out for almost nine months with a knee injury, is likely to be involved against Birmingham at Old Trafford today, while Paul Scholes, who has been absent since October, is expected to be available again by the middle of February.