Novak Djokovic faces Dominic Thiem at The O2 on Sunday as he begins the defence of his World Tour Finals title and his pursuit to reclaim the world No 1 ranking. Djokovic saw his 122-week hold on top spot ended last weekend when he was usurped by Andy Murray as the worlds top ranked player. World No 1 permutations How the No 1 ranking can change hands...again Having previously admitted that his desire and love for the game had waned, it may be that this latest development adds fuel to the Djokovic fire as he looks to win a sixth World Tour Finals and end the season on top of the standings once again. The 29-year-old has won the season-ending event the last four years and is a two-time Grand Slam champion this year, winning the Australian and French Opens to take his career tally to 14 major titles. Djokovic has endured a frustrating second half of the season and has lost his world No 1 ranking to Andy Murray He also owns a dominant 23-0 record against his three rivals in the Lendl group and first to challenge that will be the youngest man at this weeks finals - Thiem. Ivan Lendl Group Novak Djokovic (Serbia) Milos Raonic (Canada) Gael Monfils (France) Dominic Thiem (Austria) World Tour Finals: Profiles We look back on the year so far for the eight contenders Thiem too has had his struggles over the second half of the year but claimed four titles over the course of the regular season The Austrian is making his debut at the event and after a sensational start to 2016, tailed off over the second half of the year.He has never won a set against Djokovic, losing all three meetings including their most high-profile encounter at the French Open semi-final earlier this year where Djokovic won 6-2 6-1 6-4.In recent weeks the 23-year-old has suffered surprise defeats to Jack Sock, Viktor Troicki and Alexander Zverev and has not gone beyond a quarter-final since the middle of September. Introducing the underdogs What do we know about debutants Dominic Thiem and Gael Monfils However Thiem is not to be underestimated having claimed four titles this year, only Murray (eight) and Djokovic (seven) have won more although the last of those came back in June.Djokovic too has wobbled since his dominant first half of the year - he has been beaten by Marin Cilic and Roberto Bautista Agut since using the US Open final to Stan Wawrinka and he has won just one title since completing his career Grand Sam at Roland Garros and that came with victory at the Rogers Cup in Toronto in July.Whether Thiem can capitalise remains to be seen but the opening singles match of the tournament promises to be an intriguing one. World Tour Finals: The Groups We run through the contenders and their groups at The O2 As is the case for every session the doubles will kick off the action from 12pm on Sky Sports and the first match of the week will see Mike and Bob Bryan taking on Ivan Dodig and Marcelo Melo. Edberg/Jarryd Group Bob Bryan & Mike Bryan Ivan Dodig & Marcelo Melo Jamie Murray & Bruno Soares Treat Huey & Max Mirnyi Bob and Mike Bryan are five-time winners of the season-end doubles event The American brothers are seeded third this year and are four-time champions of the event but come into the tournament on the back of two years without a major title.They face sixth-seeded pair Dodig and Melo who have won the last two Masters events they have entered in Cincinnati and Canada.All the action from the O2 between November 13-20 will be live on Sky Sports across the week and if you are out and about you can follow on our Sky Sports apps and the website via our live blogs. Full schedule here. Live Tennis: ATP World Tour Finals November 13, 2016, 12:00pm Live on Get Sky Sports Get a Sky Sports pass Also See: The Groups Shots to watch Tour Finals at The O2 Panel Predictions Cheap Vapormax Nz . Barcelonas entertaining victory ensured the defending Spanish champions retained their share of the league lead with Atletico Madrid two rounds ahead of their meeting in the capital. Real Madrid needed a late goal by substitute Jese Rodriguez to earn a 3-2 victory at Valencia to stay in third place and three points behind its title rivals. Air Vapormax Nz . -- If Henry Burris has his way, he will be the starting quarterback to lead the Hamilton Tiger-Cats back to the Grey Cup next year. http://www.airvapormaxnz.com/vapormax-97-sale-nz/mens.html .Y. -- The Buffalo Sabres have recalled forward Kevin Porter and defenceman Chad Ruhwedel from the minors as part of a five-player roster shuffle made by the NHLs worst team. Nike Vapormax Plus Nz . -- PGA TOUR Canada member Steve Saunders took a three-stroke lead Saturday in the Web. Vapormax Clearance Sale . After a lengthy wait, persistent rain finally forced the postponement of the Nationals game against the Miami Marlins on Saturday night. The teams, and a few thousand fans, waited nearly four hours from the 7:05 scheduled start time before an announcement was made shortly before 11 p. LEXINGTON, Ky. -- Im a Chatterbox came through as the 2-5 favorite Sunday in easily winning the 61st running of the Grade 1, $500,000 Spinster Stakes at Keeneland to stamp her ticket to the Breeders Cup.With a perfect trip under Florent Geroux, Im a Chatterbox put the 1-1/8-mile race away shortly after straightening for home, winning by seven lengths over Paid Up Subscriber. Genre was another five lengths back in third in a field of just five fillies and mares.Ive waited a lot of years to win this race, said Larry Jones, the Kentucky native who trains Im a Chatterbox for owner-breeders Fletcher and Carolyn Gray. Its wonderful.Im a Chatterbox returned $2.80 after finishing in 1:49.98 over a fast track.Shown live on NBC Sports, the Spinster was marred by the breakdown of longshot Miss Pink Diva, who sustained a catastrophic left-hind injury upon entering the first turn. Trainer Buff Bradley confirmed afterward the 4-year-old filly had to be euthanized. Jockey Shaun Bridgmohan was not injured.Im a Chatterbox, a 4-year-old Kentucky-bred filly by Munnings, now has won 8 of 16 starts. She earned $325,000, lifting her bankroll to $2,209,614..ddddddddddddIt was her third Grade 1 victory, following the Cotillion in Sept. 2015 and the Delaware Handicap in July.The Spinster is a Win and Youre In event toward the $2 million Breeders Cup Distaff, where a formidable test awaits Im a Chatterbox. Songbird, Stellar Wind, Beholder, Cavorting, and Forever Unbridled are among the others expected for the Nov. 4 Distaff at Santa Anita.On another sun-splashed afternoon that attracted a crowd of 18,454, Paid Up Subscriber, the 3-1 second choice, grabbed the early lead from her rail post under Jose Ortiz and held a tenuous lead over Im a Chatterbox through moderate fractions. But after six furlongs, when Geroux let Im a Chatterbox loose, it was game over.The filly put me in a great position, exactly where I wanted to be, said Geroux, who continues to enjoy a breakthrough year. When she turned for home I was very impressed with her.The $2 exacta (3-1) paid $5.80 and the $1 trifecta (3-1-5) returned $4.Racing resumes Wednesday at Keeneland after a two-day break. ' ' '