Inter Milan boss Leonardo admitted he was surprised his side were forced to work so hard in their 1-0 win over Cagliari on Saturday.Inter took a seventh-minute lead through Houssine Kharja, who scored despite Andrea Ranocchia being offside.But the hosts could not capitalise on their lead and instead were forced to suffer some nervy moments towards the end as Cagliari fought for the entire 90 minutes.Leonardo said afterwards that he did not expect such a struggle."We scored the goal early on and I got the feeling we'd control the game, but we risked conceding at the end and really struggled to close down Cagliari, who have many quality players," Leonardo said."We are tired, but I don't want that to be an alibi. We've got to wipe the idea of fatigue out of our minds, as there's still a marathon ahead of us.""I honestly did not expect it to be such a struggle in this game. We started out with a team that could give us width, but couldn't really manage it.""In any case, the three points are important and we are satisfied. It's still a victory and you can win this way, with character more than skill. When you win while playing badly, it's a good sign."Cagliari boss Roberto Donadoni decided to refrain from criticising referee Domenico Celi after the match and felt his side could not have done any more."It happened, so there's no point going back over the incident now. We could talk about that forever and there would probably still be some disagreement," Donadoni said."We played a good game, but were missing that little bit of belief that would've allowed us to really get Inter in trouble. That is our only regret.""I could not have asked for any more than that from my lads and they gave Inter a lot of problems. In the first half we didn't move the ball around well enough, but really improved that after the break."Leonardo is now getting ready for his first Champions League appearance with his new club, who host Bayern Munich on Wednesday in the first leg of a round of 16 clash that doubles as a repeat of last year's final.Bayern's star duo Arjen Robben and Franck Ribery have been dogged by injuries this season but are finally back on the park together, leading many pundits to tip them to storm into contention for the Bundesliga title.But Leonardo is not worried about the club's stars and insists Bayern will have fears about facing his side."Bayern are a great side and almost all their stars are coming back from injury. Am I worried by their star names? If they read our squad list, they have reason to be worried too," he said.