Former Arsenal boss George Graham has warned Arsene Wenger he needs to spend big on up to four major stars if he is to challenge Manchester United and Chelsea again.The Gunners have been left to fight for second place in the Barclays Premier League at best as their title hopes and dreams of Champions League glory have dissolved in recent weeks. Graham, who twice guided the club to the first division championship, believes they need to raise the stakes if they are to make up lost ground on the current top two. He told BBC Radio 5 Live's Sportsweek show: 'Arsene has got to sit down and be honest with himself, which I am sure he is. 'After three-quarters of the season, they were five points clear, absolutely over-achieving, and then in the run-in, they are stumbling all the time. 'He must look back and ask: `did the players get tired? Why did they get tired? Did he have a strong enough squad? Were they too inexperienced to get over the white line and win the trophy?' 'He needs, in my opinion, three or even four ready-made players, which will cost a lot of money - and that may be a problem because I don't know if Arsenal have got a big budget to get new players in next season. 'Certain players at Arsenal keep on getting injured, and you know next season, the same players will probably be on the treatment table a lot. 'I think he needs three or four, and I think he needs three or four ready-made players, star players who are going to cost big money and big salaries, which will not go down well at Arsenal.' Asked where he feels Wenger needs to strengthen his squad, Graham replied: 'Through the middle, the spine of the team. 'They need a world-class goalkeeper, they need a centre-half, they need more mental and physical strength in the middle of the pitch. 'Unfortunately, their strikers seem to be picking up a lot of injuries, so they need somebody to play alongside (Emmanuel) Adebayor, who I think could develop into a world-class player.' At the start of a big week for English football, Graham also delivered his verdicts on the title race and the Champions League semi-finals, which see Manchester United, Chelsea and Liverpool going for glory with only Barcelona able to prevent the trophy returning to this country. Asked where his money would be on the domestic front as top two Chelsea and United prepare to meet next weekend, Graham said: 'I think it is on United. 'Both of them have got three games left and United can afford to lose one - even at Chelsea - and if they win the other two, they will still win the Premier League on goal difference.' Graham also tipped Sir Alex Ferguson's side to see off Barca and reach the Champions League final, where he has a sneaking suspicion they could meet Liverpool rather than the men from Stamford Bridge. He said: 'That is going to be an interesting one. The quality of the players Chelsea have got, I would loved to have managed them. 'But Liverpool have got the right player in (Fernando) Torres this season to play alongside (Steven) Gerrard and at last, Liverpool are now scoring goals, and they have a mean defence. 'That's a difficult one to call, it is going to be a really close one. 'I have got a funny feeling it is going to be Liverpool because Liverpool are so mean and don't give anything away, and now they have got a goal-threat up front. 'They could be out-played, but get through.'