Tenth-seeded Dimitrov, beaten by Rafa Nadal in the quarter-finals in Madrid last week,??came through against Poland’s Janowicz??6-3 7-6 (7-4) to improve to 9-3 on clay this year.
The talented Bulgarian was on top form recording only 11 unforced errors to Janowicz’s 31??to march into the second round, where he will face home favourite Fabio Fognini or American Steve Johnson.
With the temperature at the Foro Italico soaring above 25 degrees Celsius (nearly 80 Fahrenheit), fitness was key on the red clay courts and in the battle of former Wimbledon semi-finalists it was??Janowicz who made costly errors.
Gilles Simon took advantage of a few key double-faults by Jack Sock to rally to a 4-6 7-6 (7-2) 6-3 win.
Sock was up a break in the second set until his usual commanding serve deserted him. The 12th-seeded Simon quickly levelled the set and then jumped out to a 4-0 lead in the tie-breaker with the help of two double-faults by Sock.
Simon, who has won 12 ATP titles in his career, broke late in the third and closed it out at love in the final game.
Sock, a 22-year-old American ranked a career-high 33rd this week, appeared to lose energy as the match wore on and couldn’t deal with Simon’s consistency committing twice as many unforced errors as the Frenchman (48-24).
Also, Germany’s Philipp Kohlschreiber made light work of Donald Young with a comfortable 6-4 6-1 victory.