Dimitar Berbatov is an injury concern ahead of a crucial run of games for Manchester United after picking up a slight groin strain.
United's top scorer missed the midweek draw with Newcastle United due to a virus, but is now struggling with a groin problem.
He is a doubt for Saturday's Premier League game against Everton, while United also face Schalke in the first leg of the UEFA Champions League semi-finals next Tuesday.
The Premier League leaders also meet title rivals Arsenal and Chelsea in the coming weeks, either side of the return clash with Schalke.
And, though Berbatov appears to have been usurped by Javier Hernandez as first-choice striker, the Bulgarian's absence will be felt if he fails to shake off the groin problem.
However, ahead of the lunchtime encounter with Everton, Brazilian full-back Rafael is back in the squad after missing the last four games with a hamstring injury.
Ferguson also reiterated that Darren Fletcher will be thrown straight back into the fray once the midfielder is fit again after over a month on the sidelines due to a virus.
The United boss said: "Darren Fletcher is back training, he should be available again in 10 days.
"He's excelled in big games over the years. When he's fit, he'll come straight back into the team.
"Rafael is back in the squad. Berbatov has a slight groin strain, we'll see how he is tomorrow. Otherwise, everyone is fine."