Sir Alex Ferguson admits injuries to key players have had an impact but expects Manchester United to challenge for honours regardless.
The United boss feels the season ending injuries suffered by Nemanja Vidic and Darren Fletcher have impacted on his side's season to date.
However, the Old Trafford side remain in the hunt for the Premier League title and are just two points adrift of pace-setters Manchester City.
Ferguson is keen for his side to continue their fight for silverware and despite their injury problems and insists he is happy with how the season has progressed for United.
He told FIFA.com: "We've had our ups and downs and we've been unlucky with injuries. We've had a lot of them, which you don't expect, and we've got people like Nemanja Vidic and Darren Fletcher out for the whole season.
"You can replace your best players for a game or two, but you really notice the difference over a longer period, and that's what's happened to us.
"Even so, we're fighting hard to win the Premiership again and there's a lot of merit in that. Obviously I'm optimistic about our chances."
United were dumped out of the Champions League in the group stages but Ferguson insists they will come back stronger next season and mount a serious challenge for Europe's top prize.
On United's European campaign, he added: "I feel we had the ability to go all the way to the final.
"Luck wasn't on our side, but I think we've got the ambition to compete with Barcelona and Real Madrid, and I don't feel we're that far away from them.
"I'm sure we'll show that soon."
Ferguson's side will now compete in the Europa League after missing out on the Champions League knock-out rounds and United face Dutch side Ajax in Amsterdam on Thursday.