Federer skips Davis Cup training with back problems LILLE France Tue Nov 18, 2014 1:37pm EST LILLE France (Reuters) - Swiss Roger Federer's participation in the Davis Cup final against France was still hanging in the balance on Tuesday as the 17-times grand slam champion said he could not train because of back problems. Federer, however, was hopeful, although not exactly optimistic, he could be ready for Friday's first singles. It's definitely not good enough to practice. I wish progress would be faster, but we're trying hard. You know, we're heading in that direction. I feel it's definitely a little bit better than it was on Saturday night and Sunday and also Monday," Federer told a news conference in Lille, where the tie will be played on clay from Friday-Sunday. Yeah, baby steps, I guess. I'm hopeful. I mean, I hope so. Clearly I'm not going to talk exactly about what my back problem is. It's something I've had in the past. At least I'm an experienced back guy (smiling). Federer, who withdrew from the ATP World Tour final he was scheduled to play in London on Sunday against world number one Novak Djokovic, said he hoped to start training on Wednesday. "It's been a slow process," he explained. I wish I could be on the practice courts, but I can't be there yet. I'm hopeful for tomorrow. Federer leads the Swiss Davis Cup challenge with world number four Stan Wawrinka while France rely on a cluster of five top 30 players to win the competition for the first time since 2001. Switzerland have never won the Davis Cup. The French said they did not follow Federer's health problems. The important thing for us is to stay focused on ourselves, on our team. What we need is to have a perfect performance. What we can do is just play tennis. Anything else is not really our business," French number one Jo-Wilfried Tsonga told a news conference on Tuesday. Writing by Julien Pretot; editing by Justin Palmer