And why would fiery Australian tennis player Nick Kyrgios be practicing in a Gordon Hayward Celtics jersey?
The 24-year-old, known as much for his racket-smashing and chair-throwing tantrums as his tennis, is a huge Celtics fan.
Hayward responded to the US Open's tweet of Kyrgios' rocking his No. 20 jersey with his plans to watch him tonight in his opening match against American Steve Johnson.
Maybe the jersey helped as Kyrgios won in three sets, 6-3, 7-6, 6-4, to reach the second round.
Hayward, who played tennis growing up, spent some time with Kyrgios last year in Miami while the Celtics forward was rehabbing from the serious ankle injury that derailed his first season in Boston.
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