With the US Open only three days to go, here is a look at some of the players hoping to cause first round upsets at the last Grand Slam of the season at Flushing Meadows in New York on Monday.Novak Djokovic vs Diego Schwartzman
Top seed and 2011 champion Djokovic has reached the last four US Open finals but has never played the world number 80 Argentinian before. The 22-year-old 5ft 7in (1.70m) player from Buenos Aires has played just five matches on the main tour this season but qualified for the French Open where he lost to Roger Federer in the second round. His first round win over Gastao Elias in Paris is his only Grand Slam match victory. Is making his debut at the US Open having lost in qualifying in 2013.Roger Federer vs Marinko Matosevic
27-year-old Dutchman Haase is ranked 70 after reaching a career high of 33 in 2012. Hasn't played in the US hardcourt build-up to the Open, being sidelined since a first round defeat on the Kitzbuhel clay four weeks ago. Has never got beyond the third round of a major in his nine-year career and has won just one match at the US Open — in 2011 before losing to Murray in a five-set thriller in the second round.Stan Wawrinka vs Jiri Vesely
Vesely, the 21-year-old Czech left-hander, is one of the sport's highest-regarded younger players, named the ATP Star of Tomorrow in 2013 after he had started the season at 250 in the world. Now at 76 in the rankings, he has helped the Czech Republic reach the Davis Cup semi-finals this season and made the third round at Wimbledon. Made his US Open debut in 2013 but lost first round.Serena Williams vs Taylor Townsend
Five-time champion Williams is 32 now and faces 18-year-old US compatriot Taylor Townsend for the first time. Ranked 103rd, Townsend is match-tough, having made the second round in Washington — where she was runner-up to Eugenie Bouchard in 2013 — and Cincinnati in the hardcourt season. Also made the third round at the French Open. The tough, left-hander lost in qualifying at the US Open in the last two years.Maria Sharapova vs Maria Kirilenko
The battle of glamorous 27-year-old Russian blondes, former childhood friends, will ensure a busy night for press photographers. Kirilenko, a former world number 10, is down at 113 after an injury-plagued season which has seen her play just six tournaments and saw the end of her engagement to Russian ice hockey star Alex Ovechkin. Sharapova and Kirilenko once played doubles together, winning a title on grass in Birmingham 2004 on the eve of Sharapova's breakthrough Wimbledon title.Petra Kvitova vs Kristina Mladenovic
The 73rd-ranked Mladenovic has enjoyed Grand Slam title success, winning the mixed doubles at Wimbledon in 2013 and this year's French Open with Daniel Nestor. Made the third round of the US Open singles in 2012 where she lost in straight sets to compatriot Marion Bartoli.
(Graphics by Vignesh Radhakrishnan)