Before each day of play in Toronto and Montreal, we'll preview and predict three must-see matches.

The one full-fledged star in the men’s draw finally makes his singles debut on Wednesday. In his two matches against Muller, Djokovic hasn’t dropped a set, and there’s no serious reason to think he will this time. Muller is 33 years old and ranked 37th. But his heavy lefty serve can make him a tough out for anyone. And an early struggle in Toronto wouldn’t be unprecedented for Djokovic, who lost in the third round to Jo-Wilfried Tsonga here two years ago. But the Olympics mean a lot to him, so I can only assume he’ll be eager to build some momentum for them here.

Winner: Djokovic

If their last two matches are any indication, this could be an epic; each has gone to 7-5 in the third set. Each of them also ended in a Venus victory; the American is 3-0 against the Czech. Venus has been on something of a roll lately. She was a quarterfinalist in Paris, a semifinalist at Wimbledon and a finalist in Stanford this past weekend. On paper, the sixth-ranked Williams will be the favorite against the 22nd-ranked Strycova. But at some point Venus has to get just a little bit tired, right?

Winner: Williams

Is the post-Zverev generation upon us already? Shapovalov is a 17-year-old Canadian who won the boys’ title at Wimbledon this year, and stunned Nick Kyrgios in his night-match opener on Monday. Shapovalov will be back out at night, in what seems to be another winnable match. Dimitrov obviously has the experience and the polish, but Shapovalov has the hunger and the energy, and he’ll have the crowd. His lefty forehand may not remind you of Rafael Nadal, but his lefty fist pump might.

Winner: Dimitrov