And after noticing that Errani's previous opponent, Mirjana Lucic-Baroni, tried unsuccessfully to pound those soft serves, Wozniacki decided the best course of action was simply to make sure she put those balls in play.
Getting all 34 of Errani's serves back over the net, and then claiming 26 of those points, Wozniacki parlayed six breaks and a 26-12 total edge in winners into a 6-0, 6-1 victory over the 13th-seeded Errani in a wind-whipped match Tuesday night.
The victory for the 10th-seeded Wozniacki moved her into her first Grand Slam semifinal in three years.
''I learned quite a lot from Lucic the other day. She was going for every return and trying to make winners on every return,'' Wozniacki said. ''For me, that wasn't really the game plan today. It was just putting pressure on her from the start, and kind of start the rally from there.''
Italy's Errani averaged only 65 mph (105 kph) on second serves, and 78 mph (126 kph) on first serves, and that was a problem.
''I hoped she would miss something here and there,'' said Errani, who beat Venus Williams in the third round, ''but today she practically never missed.''
With the players' towels and spectators' napkins and all sorts of things being tossed around by the stirred-up air, Wozniacki dealt with the conditions far better than Errani. Although not right away.
The match began competitively enough, with a pair of points that lasted more than 20 strokes apiece in the first game. Errani earned four break points before 2009 U.S. Open runner-up Wozniacki eventually held despite a double-fault in which one serve didn't come close to reaching the net.
''I have played in some very windy conditions here, but I know how to adapt,'' said Wozniacki, the runner-up at the U.S. Open in 2009, and a semifinalist in 2011. ''It just took me a few serves to kind of get into the rhythm and figure out where to throw the ball and what to aim for.''
Wozniacki, a former No. 1 who eliminated five-time major champion Maria Sharapova in three sets in the fourth round, will face unseeded Peng Shuai of China in the semifinals.
Errani was a finalist at the 2012 French Open, and made it to the final four at that year's U.S. Open, too.
She's accustomed to outrunning opponents on court and wearing them down. On this night, Wozniacki - who has been training to run the New York City Marathon in November for charity - did that very thing to Errani.
''Maybe,'' Errani said with a chuckle, ''I need to run the marathon, too.''