Surprise package Davidovich Fokina, who knocked out top-ranked Novak Djokovic and Indian Wells champion Taylor Fritz in the earlier rounds at Monaco, drew first blood by breaking Tsitsipas to take a 2-1 lead in the opening set.
Big-serving American Andy Roddick eased past former world No 1 Juan Carlos Ferrero to make the semi-finals of the China Open on Friday, along with Germany's Bjorn Phau, Israel's Dudi Sela and Rainer Schuettler of Germany.
Lleyton Hewitt beat Spaniard Juan Carlos Ferrero 7-6, 6-4 in the first round of the Montreal Masters.
Serb Ana Ivanovic saved three match points in overcoming fellow teenager Nicole Vaidisova 4-6, 6-2, 7-5 in the quarter-final.
The Swiss beat David Ferrer 6-4, 6-0 at Monte Carlo Masters to clinch his 500th professional win.
Rafael Nadal said on Monday he expected to lose his world number two ranking to Serbia's Novak Djokovic by Wimbledon at the latest.
World number two Rafael Nadal's bid to win the Rome Masters for the fourth successive year was buried on Wednesday when he lost 7-5 6-1 to Juan Carlos Ferrero.
Seventh seed Juan Carlos Ferrero made a surprise first-round exit from the World Indoor Tournament in Rotterdam on Monday after a 7-5, 6-1 defeat by Russian qualifier Teimuraz Gabashvili.
Justine Henin and Maria Sharapova set up an explosive Australian Open quarter-final with crushing wins.
Second seed Fernando Gonzalez and defending champion Ivan Ljubicic both suffered quarter-final exits from the Vienna Open on Friday, leaving world number three Novak Djokovic as the tournament's only remaining seed.
Juan Carlos Ferrero and David Ferrer gave champions Spain a 2-0 lead over Israel with crushing singles victories on the opening day of their Davis Cup World Group semi-final on Friday. Roared on by the boisterous home support in Murcia, former world number one Ferrero thumped Dudi Sela 6-4, 6-2, 6-0 after Ferrer had earlier thrashed Harel Levy 6-1, 6-4, 6-3.
Juan Carlos Ferrero's struggle for form continued at the Marseille Open on Tuesday where the former world number stumbled in straight sets in the first round against Joachim Johansson.
Juan Carlos Ferrero ventured into uncharted territory at Wimbledon on Tuesday when he beat Serbia's Janko Tipsarevic 7-5, 6-3, 7-6.
The organisers of European Masters Series tournaments will meet in Paris on Tuesday to discuss ways to curb the number of withdrawals by leading players.
Former world number ones Lleyton Hewitt, Juan Carlos Ferrero and Marat Safin moved smoothly into the second round of the Hamburg Masters on Monday but last year's runner-up Radek Stepanek fell to Arnaud Clement.
Roger Federer once again conceded defeat to arch-rival Rafael Nadal when he and his fellow Swiss Stanislas Wawrinka lost to Nadal and Carlos Moya.
Second seed Rafael Nadal beat fellow-Spaniard Juan Carlos Ferrero, while Andy Roddick got past France's Richard Gasquet at the Pacific Life Open.
Guillermo Canas won his first tournament since a 15-month doping ban when he claimed the Brazil Open.
The world No. 3 said he wants tp play in the Athens Games next year, because at 28 he has a good chance of winning a medal.\n\n
Reigning champion and ninth seed Juan Ignacio Chela was knocked out in the first round of the Estoril Open.
Andy Roddick and Juan Carlos Ferrero will contest the Cincinnati Masters final on Sunday.
Ferrero will meet fellow-Spaniard Tommy Robredo, who upset third seed Ivan Ljubicic of Croatia 7-6, 6-2 to reach the semi-finals of the Cincinnati Masters.
Nadal will meet defending champion Guillermo Coria in the final of the Monte Carlo Masters.
The move is designed to favour 2002 Wimbledon champion Lleyton Hewitt and this year's runner-up Mark Philippoussis.
Agassi remains top of the 12-month rankings with 4,090 points followed by Ferrero and Federer.
Former French Open champion Albert Costa bowed out of professional tennis, losing to fellow-Spaniard Juan Carlos Ferrero in the third round of the Barcelona Open.
Juan Carlos Ferrero made a confident start to his title bid in Barcelona when he thrashed Kristof Vliegen 6-1, 6-2
Spaniards David Ferrer and Juan Carlos Ferrero also suffered first round shocks at the Valencia Open on Tuesday.