Sir Alex Ferguson has stated he chose to rest Nemanja Vidic for Manchester United's Champions League round of 16 first leg tie against Real Madrid at the Bernabeu in midweek, as there was an injury risk involved in handing the player two starts in the same week.

Nemanja Vidic

The Red Devils skipper, who produced an impressive performance against Everton last week, was a surprise omission from Ferguson's starting line-up against Los Blancos. The Scot has now revealed the Serbian's recent injury record prevented him from giving the defender back-to-back starts for the first time since September.

Vidic, who has spent a large amount of time on the treatment table in the last few seasons, returned to the United squad only recently, following his battle with knee problems over the past 14 months.

"Three days after Everton was a risk," Ferguson said. "We tried to manage Nemanja and Rio [Ferdinand] and if he had that extra day he would have been alright, but just three days after playing on a really heavy pitch at Old Trafford it was maybe a bit of a miss for us but I can't take a risk," the manager pointed out.

Ferguson also showered praise on Cristiano Ronaldo, after watching the Real Madrid talisman score against his former club.

The Portugual forward rose above Patrice Evra, around the half-hour mark, to head home an Angel di Maria cross, to level the scores after Danny Welbeck gave the Red Devils an early lead at the Bernabeu.

Ferguson and Ronaldo

"What a header. Unbelievable. You can't stop that, the leap and the spring to hold himself in the air. I said to Patrice Evra at half time, 'why didn't you challenge him?' and then I saw the replays and then thought 'what was I talking about?'" Ferguson said.

"I think it was difficult for him playing against an old team, and it had a little bit of emotion attached to it because he played for us for six years, but he was still a big threat for them. When he gets the ball you are praying more than anything," the 70-year-old added.