Britain's James Ward posted his first ever win at a Masters series event to reach the second round of the Western & Southern Open in Cincinnati.
The British number two beat two top-100 players in qualifying and defeated a third in Spain's Guillermo Garcia-Lopez in round one.
Ward, who will now play either Julien Benneteau or Blaz Rola, recovered from losing the second set to triumph 6-2 3-6 6-1 against the world number 32.
Ward has had a good run on the North American hard courts at second-tier Challenger level and carried that form into Tuesday's match.
Garcia-Lopez, in contrast, was on a four-match losing run and his lack of confidence showed in a lacklustre opening set.
Ward then missed eight break points in the first game of the second and was made to pay as Garcia-Lopez levelled the match.
But the British player responded superbly with a solid deciding set, winning the first five games and clinching victory on his first match point.
Ward is only 11 places adrift of his highest ever ranking of 137 and has already guaranteed himself US dollars 21,945 in prize money.
Novak Djokovic had to dig deep to fend off Frenchman Gilles Simon in the second round.
Serbia's world number one appeared in trouble after dropping the second set to Simon but he recovered to post a 6-3 4-6 6-4 win.
Djokovic, afforded a first-round bye, told the ATP website: "I know I'm not playing at the level yet where I want to be and it's obvious, but I keep on pushing myself.
"Every day is a new challenge to try to look out for a better game tomorrow and after tomorrow, and hopefully it's going to come."
Djokovic has a particular target this week, which is to land the title and become the first singles player to complete a career sweep of all nine World Tour Masters 1000 tournaments, the tier below grand slam level.
Elsewhere, there was disappointment for 12th seed Jo-Wilfried Tsonga as he lost out in the first round to Mikhail Youzhny.
The Frenchman was coming off the back of his victory in Toronto last week but was brushed aside 6-1 6-4 by the Russian who will next face Andreas Seppi, a 4-6 6-2 7-5 victor over Santiago Giraldo.
In the second round, third-seed Stan Wawrinka beat Benjamin Becker 6-3 7-6 (7/5).
Marin Cilic set up a second-round tie with Fernando Verdasco as the 14th seed beat Feliciano Lopez 6-3 6-4 and Vasek Pospisil was a 5-7 6-1 7-6 (7/4) winner over Radek Stepanek.
Ninth-seed Ernests Gulbis needed two tie-breaks to beat Ivan Dodig 7-6 (10/8) 7-6 (7/4) while Roberto Bautista Agut defeated Martin Klizan 6-2 4-6 7-5.
Robby Ginepri overcame Dominic Thiem 6-3 5-7 7-5 and Julien Benneteau beat Blaz Rola 6-7 (7/9) 6-3 7-6 (9/7).