"We showed strength again on Saturday [against Sheffield United], even though we played with some players who didn't play against Barcelona and we're really progressing," said the striker.
"I think we're better playing now after Champions League games than we were before.
"It seems to have been difficult for us to pick ourselves up after European games. But we've got a good squad of 22 players and, if it's necessary to use them, we can.
"We've got to go on playing like this, finish this year as high as possible in the league, and we're still in the Champions League. So we've got to go on and see what happens. Europe is very important for us."