Heavy downpours suspended opening day play on the outer courts at the Australia Open, but a lot of the action played out under the roofs. Here are the Top 5 photos from Monday. (All photos from Getty Images.)

1

In their second career meeting, Coco Gauff beat Venus Williams, 7-6 (5), 6-3 (she also won their Wimbledon opener). Gauff, who at 15 is the youngest player in the draw, will take on Romanian Sorana Cirstea in the Australian Open second round. 

2

Roger Federer opted to not play in the inaugural ATP Cup and didn't compete in any warm-up tournaments, but he looked to be in fine form on Monday. He eased passed American Steve Johnson, 6-3 6-2 6-2, in front of his family, including both sets of twins. 

3

Rain hit Melbourne and suspended much of the event's first-round play. Hours after Day 1 kicked off, umbrellas went up and fans scurried to find somewhere dry to hide. The Grand Slam now faces the prospect of backlogged matches, but the wet weather is a huge relief for the bushfires. 

4

Grigor Dimitrov suffered a shaky first set to defeat Juan Ignacio Londero, 4-6, 6-2, 6-0, 6-4. The No. 18 seed, who reached the Australian Open semifinals in 2017, will next face the winner of Tommy Paul and Leonardo Mayer. 

5

Naomi Osaka had a great day at the office by defeating Marie Bouzkova in straight sets to start her title defense. She lost just six games, and heads into her second-round match against Zheng Saisai in confident form.