The Swiss former world number one was unable to end a seven-year losing streak to Nadal in Slams, and said that his biggest regret will be not being able to take on his compatriot Stanislas Wawrinka in Sunday's final.
"It's very encouraging, no doubt," he said after the match against Nadal. "I wish I could have won here tonight and given an all-Swiss final. That's something I'll regret for a long time.
"I think this is a very good start to the season for me overall. I played some really good tennis here. I still feel my best tennis is only ahead of me right now.
"So I'm looking forward to the next couple of months, how they're going to play out and hopefully by April I feel like I'm going to be at 100% again."
Federer's last Slam was Wimbledon in 2012.