Onward and upward to day three of the Barclays ATP World Tour Finals, which saw David Ferrer beat a hobbled Andy Murray and Novak Djokovic struggle against an in form Tomas Berdych.

The Ferrer result certainly changed how the group was projected to work out and Djokovic is certainly the clear favorite to win the group from here.

But let's rewind to the beginning of the day, shall we?

It was another especially foggy day in London, which made for shooting my very short preview video for tomorrow's Group A singles matches quite difficult. Yet we did it and I bounded off to record Rafael Nadal's practice on the sponsor centre court.

The Spaniard was scheduled to start at 1 p.m. and he had the court until 3 p.m. At first, I thought the schedule was wrong because Nicolas Almagro was on the court with his team. He was apparently killing time, as he was playing what looked like a combination of miniature golf and bocce with someone on his team.

Almagro seemingly won the first game, which gave him the right to hit serves from the service line at his compatriot. They did play long enough for Almagro to lose, but his opponent couldn't make good on the chance to hit peg him.

Soon after that, Almagro left. About 45 minutes after I arrived, a group of the Spanish press arrived and hung out near the entrance of the court.

At that point, I figured his arrival was imminent. After all, his practice partner had shown up and went through his warm-up routine, but by 2:30 p.m. Nadal still hadn't arrived.

I found out later that he showed up around 15 minutes after I left and, according to a security guard I'm friendly with, practiced for about 10 or 15 minutes before suddenly stopping.

His lack of practice is understandable. After his win against Mardy Fish last night, Nadal said he was struggling with a stomach illness of sorts, which does a number on your endurance.

Nadal's lack of practice could be a huge hindrance in his match against Roger Federer tomorrow night. All that being said, the ATP told me it's not unusual for a player to not show up to his scheduled practice, so we'll have to wait until tomorrow night to see.

Speaking of Roger, the Swiss had a one hour and 30 minute practice session on one of the outside courts in the Fanzone.

I wanted to at least grab some photos of it, but the David Ferrer press conference ended at 5:20 p.m., which left me about half an hour to run across the O2 Arena's grounds to where Federer was, get some video, and come back for Andy Murray's interview.

As I arrived at a balcony overlooking the Fanzone, you could tell something big was going on. The two courts are in what looks like a miniature aircraft hanger, with open viewing space on one end and a set of french doors as the only entrances.

Federer was on the court to the left, and there were dozens of people lined up just at the precise angle at the door to watch him and take photos. If people weren't leaning over each other, they were sitting on someone's shoulders just for a chance to see the 16-time Grand Slam champion knock some balls around.

I'm sure they would have loved to go in, but the stands were completely packed. I, however, had a relatively free space to move about in, and I was able to get some video without standing in the way of the fans.

I don't think any tennis player truly transcends national boundaries like Federer does. Sure, being the most prolific Grand Slam winner in the Open Era doesn't hurt his likability any, but he's got something else that really captures people's attention.

What I'm saying is that, even in a Davis Cup final against Djokovic in Serbia, I'm sure he would have a (relatively) friendly crowd.

In his practice, Federer showboated a bit for the crowd, including hitting a lackadaisical two-handed backhand lob that found it's way in (which drew a healthy amount of applause).

So to summarize: Federer looks in pretty good shape and Nadal is a huge unknown. Hopefully he feels better tomorrow, as it would be a real shame if a stomach problem disrupted what has been a pretty good season.

Besides, as a tennis fan, it would be great to see both men at their best.

Below you can see the video of Federer's practice.