Andy Murray, who claimed his second title of the season in Vienna last week, defeated Austria's Jurgen Melzer 6-3, 6-3.
John Tomic, who also coaches Bernard, is barred from tournaments by the ATP and International Tennis Federation.
Melzer was leading 6-3, 2-1 -- and was up a break in the second set -- when Monfils called it quits with an abdominal muscle injury.
The French 15th seed defeated 10th-seeded Ukrainian Alexandr Dolgopolov 7-6 (11/9), 6-3 while Jurgen Melzer defeated
Fognini led 4-1 before dropping serve in the third. He held on and became the first Italian champion in Stuttgart.
Andy Murray breezed past Spanish veteran Tommy Robredo, the 32nd seed, 6-2, 6-4, 7-5. Sergiy Stakhovsky, the world number 116, who sent seven-time champion Federer crashing out in the second round, went down 6-2, 2-6, 7-5, 6-3 to experienced Austrian Jurgen Melzer.
After the highs of beating Roger Federer at Wimbledon, Stakhovsky was brought back down to earth after he slumped to a 6-2, 2-6, 7-5, 6-3 loss to Jurgen Melzer.
Stakhovsky, who became an Internet hit last month for whipping out his mobile phone to take a photo of a controversial line call on the clay of the French Open, has four tour titles to his name. He was also 31 in the world three years ago.
Mahesh Bhupathi-Julian Knowle beat Argentine-Spanish duo Leonardo Mayer and Albert Ramos 6-2, 6-7(5), 6-4, 6-2 in two hours and 37 minutes in the first round clash.
Seeded ninth, Paes and Melzer fought hard before going down 7-5 4-6 6-7(6) against unseeded Uruguan-Argentine duo of Pablo Cuevas and Horacio Zeballos in little less than two-and-a-half hours at the Roland Garros.
Seeded fourth, Bhupathi and Bopanna had a forgettable outing at the Roland Garros last night as they were stunned 5-7 4-6 by unseeded Polish combination of Tomasz Bednarek and Jerzy Janowicz.
Bhupathi and Bopanna, who rejoined forces after splitting, next face unseeded Czech pair of Tomas Berdych and Radek Stepanek.
Leander and Melzer were off-colour today as Haas-Stepanek pair broke their service on four occasions which was testimony to the supremacy of the German-Czech duo.
Nadal will play a Saturday semi-final against Canadian fifth seed Milos Raonic, who beat Ernests Gulbis 6-2, 7-6 (8/6) and followed up by winning a hard-fought battle with Spanish veteran Tommy Robredo 6-7 (5/7), 6-3, 7-6 (7/2) in almost two and a half hours.
In the deciding super tiebreak, the unseeded men were no match for the Bryan brothers who easily raced away to 10 points and will now face Canada-Australian pair of Milos Raonic and Bernard Tomic in the last four Saturday.
Unpredictable Italian Fabio Fognini sprung a surprise on fourth seed Tomas Berdych, dismissing the Czech 6-4, 6-2. French sixth seed Jo-Wilfried Tsonga thrilled his home fans as he overwhelmed Austrian Jurgen Melzer 6-3, 6-0.
Sixth-seeded Jo-Wilfried Tsonga also advanced, beating Jurgen Melzer 6-3, 6-0. The Frenchman will next face either second-seeded Andy Murray or No. 13 Stanislas Wawrinka.
Bhupathi and Bopanna, who announced earlier this month that they would team up yet again, were given a bye in the opening round at the 2,646,495 Euro clay court event.