It's National Coffee Day (for whoever acknowledges such things) so it's only fitting to remember the time Serena Williams ordered an espresso mid-match. Back in January of 2015, before Williams won three of the year's majors and Flavia Pennetta won the US Open (and then retired), the two faced off in the Hopman Cup.

After dropping the first set 6-0, Williams needed a little pick-me-up. "I don't know if it's allowed," she said. "Is it allowed?"

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The caffeine seemed to help as Williams bounced back to beat Pennetta in three sets.