It was easy to say who drew the toughest group long before the draw was made in London on Thursday for the ATP World Tour Finals. It would clearly be whoever was matched up with top-ranked Novak Djokovic.
That was the Stan Smith group, which also includes Roger Federer, Tomas Berdych, and Kei Nishikori. The other group, named for Smith's rival Ilie Nastase, is led by No. 2-ranked Andy Murray. Also in that group: Stan Wawrinka, Rafael Nadal and David Ferrer.
Djokovic is 78-5 in 2015 with 10 titles (he's on track to post the fifth-best single-year winning percentage of the Open era). He'll be looking to secure his fifth overall and fourth consecutive year-end tour championship, on a hard-court surface that is tailor-made for his kaleidoscopic, all-purpose game.
Can anyone stop him? Let's take a look at the seven challengers, in ranking order:
No. 2 Andy Murray
The Scot will be hoping to lead Great Britain to a landmark Davis Cup triumph the week after the World Tour Finals, which could be either a distraction or a factor that relaxes and frees him to play his best tennis.
Murray spent the early part of this week practicing on the clay at Queen's Club (for the Davis Cup tie against Belgium). Will he have enough time to dial in his hard-court game, and will he be willing to leave it all out there in potentially long matches? These are relevant question because this promises to be a very competitive group.
Murray has lost to just one player since the US Open. You guessed it: Djokovic, who beat him in the finals of the two big fall Masters 1000 tournaments.
No. 3 Roger Federer
The Swiss icon isn't accustomed to playing the role of the spoiler, but after losing to Djokovic in the finals of two majors this year, that's exactly where the 17-time major winner finds himself. Berdych and Nishikori are manageable opponents, so even if Federer loses to Djokovic in the round-robin portion, he could get another crack at the world No. 1 if they both advance.
Federer has been more effective than anyone else against Djokovic this year (2-4); he thrives on indoor hard courts; and he's won this event six times. That ought to raise some red flags for Djokovic. Playing a limited schedule since his loss to Djokovic in the US Open final, Federer has won one event, the ATP 500 in Basel.
No. 4 Stan Wawrinka
This is an excellent opportunity for Wawrinka to add to his résumé and build on his credibility as the man who broke up the Big Four. This is his third consecutive appearance at the WTF, and he's made the semifinals on both previous occasions.
Wawrinka has improved dramatically on hard courts over the past two years. This year he lost to Federer in a US Open semifinal, and he won the ATP 500 in Tokyo.
No. 5 Rafael Nadal
"I'm trying," Nadal said, when the host of the ATP draw ceremony observed that his game appeared to be getting better in this otherwise off year for the 14-time Grand Slam champion. Nadal's immediate problem is that this is the only significant hole in his résumé; his best finish in the tour championship was a pair of runner-up conclusions (2010 and 2013).
Nadal has battled a sometimes dreadful slump most of this year. He will be trying to sustain the momentum he's built over the course of a solid fall in which he made the finals of two ATP 500 events, Beijing (loss to Djokovic) and Basel (loss to Federer).
No. 6 Tomas Berdych
People have waited a long time for the rangy 6-foot-5, 30-year-old Czech to get it together. Could this, his seventh appearance in the WTF, be the year he makes a breakthrough? It's unlikely, with Djokovic and Federer in the same group, but Berdych has won a Masters 1000 (Paris Indoor) under similar conditions.
Berdych has had a good fall. Since a poor US Open, he's won a pair of ATP 250s (Shezhen and Stockholm) and his losses in the two Masters were to Murray in Shanghai and Djokovic in Paris.
No. 7 David Ferrer
The "Little Beast" has a solid chance to make the semis for the third time in his career. His consistency and grit could cause problems for Nadal, and, if given the opportunity, he'll run Wawrinka all over the court. Murray, however, is undefeated in his past four matches with Ferrer dating back to the start of 2014.
Ferrer is in the midst of a late-season surge. Since the US Open, he's won the Kuala Lumpur 250 and the Vienna 500.
No. 8 Kei Nishikori
A semifinalist in his WTF debut last year, Nishikori will be lucky to match that result. He's struggled ever since he lost to Benoit Paire in the first round of the US Open. He reached the semis in Tokyo, losing to No. 32 Paire again, but he failed in two consecutive matches again after that for the rest of the year.