Iga Swiatek progressed smoothly into the Wimbledon third round on Thursday at the expense of Croatia’s Petra Martic, racking up a 21st straight win. A single break in the first set put the Polish top seed in charge and she repeated the feat in the second set to seal a 6-4, 6-3 victory. Martic needed treatment for an apparent lower back issue midway through the first set of the second-round match on Centre Court before resuming with no apparent discomfort. Swiatek broke her 85th-ranked opponent in the 10th game to take the first set 6-4. Martic battled hard in the second set but Swiatek ultimately had too much power, breaking in the eighth game from 40-0 down and serving out to love for the win. Swiatek hit 25 winners against 19 unforced errors in the match, which lasted 83 minutes. The top seed, who has never been beyond the quarter-finals at Wimbledon, is chasing a sixth Grand Slam title following her recent French Open triumph.