Forlan was bought towards the end of the summer from Atletico Madrid, but he was ineligible for the group stages having represented the Spanish side in a third round qualifying fixture.
"I was missing it," admitted the Uruguayan in an interview with UEFA.com.
"This competition is the most important in the world and I'm looking forward to playing in it again. Now I can and we are already in the Last 16.
"What I have always tried to do for all the teams I played for as a striker, is score goals. And also, now that I play a bit deeper, I can also help out defensively and give support there."