NEW YORK — A day before facing Venus Williams — and a partisan crowd — at the U.S. Open, Italy’s Sara Errani came across a video posted on Twitter that gave her a little extra motivation.

It showed a pair of former players and coaches, Brad Gilbert and Darren Cahill, forecasting Friday at Flushing Meadows. Both picked Williams to win.

The 13th-seeded Errani’s ears perked up particularly when Gilbert referred to her “cottage cheese” serve and predicted she’d win only four games.

So much for that. In a riveting third-round match of wild momentum swings, the 19th-seeded Williams, a two-time U.S. Open champion, came within two points of victory four times before succumbing to Errani 6-0, 0-6, 7-6 (5).

As if needing a reminder of what she’d seen online, Errani was interviewed for TV by Cahill before the match, and by Gilbert afterward.

“Let’s just say that during the match I thought about that (video) more than once,” said Errani, who pounded her chest with a fist and put a finger to her lips on court as if to hush doubters.