Sir Alex will face a serious selection dilemma should Jonny Evans be ruled out of United’s Champions League clash with Inter Milan on Tuesday.

The young defender limped off against Blackburn Rovers on Saturday evening with a reccurrence of a recent ankle injury.

“It’s a bit sore,” Evans told MUTV after the final whistle. “I kicked the ground when I tried to make a long clearance and now it’s a bit tender.

“I don’t know [if I’ll be ready for Tuesday’s game]. The doctor said he’d have a look at it on Sunday. We’ll have a better idea then.”

The Reds were always going to face the Italian champions without the suspended Nemanja Vidic, but Sir Alex was counting on Evans to plug that gap. Gary Neville and Wes Brown are also out injured, further curtailing the manager’s options in the centre of defence.

“We’ve got some injury issues,” the boss told Setanta Sports. “I just hope I can get two centre-halves fit for the match. At the moment it’s doubtful.

“I’m hoping I’ll have John O’Shea fit as I won’t have Vidic, Neville or Brown either.”

O’Shea injured his heel against Fulham last Wednesday but if neither he nor Evans is fit for Tuesday, the boss could be forced to emply unconventional measures.

On MUTV's Matchday Review programme, United legend Lou Macari said he thought Sir Alex might play Rafael on the right, his brother Fabio on the left and bring Patrice Evra into the middle to partner Rio Ferdinand.

Sir Alex Ferguson says United's 2-1 win over Blackburn shows the Reds must “fight for our lives” to win the title.

United can expect 12 more battles to clinch an 18th league title. Wayne Rooney put the Reds in front, but Roque Santa Cruz levelled for a spirited Rovers team, and it took a fabulous free-kick from Cristiano Ronaldo to seal the win.

“It was a great lesson for us,” said Sir Alex. “It tells you what this league is like. There’s no way we can forecast winning the league when you get difficult games like this. Blackburn are down at the bottom, they’re going to fight for their lives. That’s what you expect from every team in the bottom eleven. It’s a difficult league.

“A lot of people are talking about us winning the league, but we must dismiss it. This was a great reminder that we’re going to have to focus on every game. Just as the teams at the bottom are fighting for their lives, we have to fight for ours.”

Sir Alex wasn’t wholly convinced by his team’s display. “We probably just deserved it, but only just,” he added. “We were in a controlled position and gave away a goal. When you consider the way we’ve defended over the last ten weeks or so, that was not indicative of our performances. It was a very soft goal to give away. Blackburn got a lot of resolve from that. They became very determined in the second half, they put on a great show and Sam will be pleased with them. They made it a real fight.”

But winning tough matches is a quality all champions possess. “Sometimes when you don’t play at your very best, you can get a result like that and it hopefully goes towards winning the title,” he said. It certainly looks good, now eight points clear. But the United boss won’t be counting his chickens yet.

Cristiano Ronaldo was pleased to grab the winner to send United eight points clear at the top of the Premier League.

Ronaldo conjured one of his special free-kicks to clinch a hard-fought and, he says, deserved 2-1 win.

“The most important thing is that we are top of the table and now we are eight points ahead of Liverpool,” Ronaldo told MUTV.

"I’m very happy that we got three points. It was a very tough game. The manager said before the game that it was going to be one of the toughest games of the season. He has experience and he knows better than anyone. We saw in the game that Blackburn created chances and they were a dangerous team playing on the counter attack.

“We controlled most of the game and had more opportunities. At the end of the day I think we deserved to win because we looked to score goals.”

Ronaldo felt that he was unfairly singled out for diving, when Rovers midfielder Morten Gamst Pedersen also took a tumble in the box and got away with it. “I thought Pedersen dived. It wasn’t a penalty. Pedersen dived and didn’t get a yellow card, but I dived and he did book me! But I suppose that’s just the situation of the game.”

But ultimately Ronaldo’s most important contribution was his goal after an hour. The free kick from the corner of the penalty area was struck with such venom and speed that Paul Robinson saw it late coming through a crowd of bodies. The Portuguese winger was pleased with the importance of the strike as much as how it looked.

“I was pleased with my goal, it was a good free kick and an important goal. I’m looking forward to seeing it on television!”