US Open champion Stanislas Wawrinka faces Japan's Kei Nishikori on day two of the ATP World Tour Finals at The O2 Arena in London.
Where to watch live
Wawrinka vs Nishikori starts at 2pm GMT and is live on Sky Sports 1HD, BBC Two HD and BBC Radio Five Live sports extra.
Stanislas Wawrinka and Kei Nishikori bid to end contrasting seasons on a winning note when they begin their ATP World Tour Finals campaign at The O2 Arena. The world number three and five have enjoyed decent success in London during their previous appearances but are each yet to reach the final at the season-ending tour finals.
US Open champion Wawrinka has reached the semi-final on each of his three appearances in Greenwich, twice losing to Roger Federer and once to Novak Djokovic. The Swiss will be eager to maintain his 100% record in progressing from the round robin stage - though his recent form means he arrived in the English capital far from his best.
Since beating Djokovic in four sets at Flushing Meadows, Wawrinka has won just six matches in his next four tournaments. That run included early exits at the Masters Series events in Shanghai and then Paris, where he lost in three sets to world number 91 Jan-Lennard Struff.
Wawrinka endured a torrid grass court season, losing to Juan Martin del Potro in the second round at Wimbledon while he was ousted from the Australian Open by Milos Raonic. The ebb and flow of the 31-year-old's campaign means he may well be the underdog in a strong looking group which also includes Andy Murray and Marin Cilic.
Nishikori has meanwhile identified his Davis Cup loss to Andy Murray in March as the moment his campaign turned around. Since that five-set loss in Glasgow the Japan number one reached the final at the Miami Masters and Montreal Masters, and won bronze at the Rio 2016 Olympic Games.
But since those heroics in Brazil Nishikori has suffered some damaging defeats, being defeated in the final in Basel to group rival Cilic before defeat to Jo-Wilfried Tsonga in Paris. The 26-year-old reached the last four on his first ATP Finals appearance but last year was thumped by Djokovic and Federer and failed to make the knock-out stage.
What the players say
Stanislas Wawrinka: "This is an amazing tournament for every player. It was always a dream for me to play in this tournament, so to finish my year playing here is very enjoyable. It was my goal at the beginning of the year to make it back, so I'm pleased to be here and I want to make the most of it.
"[Nishikori] he's a tough player. The conditions here are very fast, so it's important for me to try and be aggressive, put a lot of pressure on him and push him back. I need to try and make it a physical battle.
"It's always a challenge for a coach to find the best way to make the most of a player," said Wawrinka. "He's tough, but I'm also tough on myself. We've been working really well together so far and have had some amazing results, so hopefully we can keep working for a few more years."
Kei Nishikori: "It's a very tough group. I'm playing Stan, who is having a great year, in my first match. Andy is the new number one and Marin is also in form. But I'm getting used to playing here, this is my third appearance, and it is a big goal for me to do well. It is a great opportunity for me to finish a great season.
"The Davis Cup match was a turning point for me, even though I lost the match against Andy. I didn't feel I had much of a chance to win, although I almost beat him [in five sets] and it gave me a lot of confidence. To beat him at the US Open was my second win over him. It showed me that I could play with a lot of patience and confidence over five sets. I was able to play good tennis."
Betting odds (source Betfair):
Stanislas Wawrinka 1/1 vs 5/6 Kei Nishikori
Head-to-head record: Wawrinka 4-2 Nishikori. Last match US Open (hard) Wawrinka bt Nishikori 4-6 7-5 6-4 6-2
Previous meetings at the ATP World Tour Finals: N/A