The decline in the number of tournaments in the U.S. corresponds with the decline in the number of highly ranked Americans and the growth of tennis in Europe and Asia.
Federer, 37, defeated 19-year-old Denis Shapovalov, and John Isner, the defending champion, got past 18-year-old Felix Auger-Aliassime.
Felix Auger-Aliassime, a Canadian qualifier, is the youngest man to reach the semifinals in the tournament’s history.
After cruising past Daniil Medvedev, Federer will face off against Kevin Anderson in his quest to win this tournament for the first time since 2017.
Seemingly on a roll after winning the Australian Open, Djokovic, who has been embroiled in a back-room ATP imbroglio, stumbled for the second time in two weeks.
The South Florida tennis tournament has developed into the de facto Latin American Slam, drawing passionate fans from the region and its diasporas.
Federer got off to a slow start before crushing Filip Krajinovic. Andreescu, coming off a win at the BNP Paribas Open, pulled out because of a shoulder injury.
Mari Osaka, ranked 338th, is the big sister of Naomi, and she got a wild-card entry, playing her first WTA main draw match on Thursday. She acquitted herself well in a 6-2, 6-4 loss.