At this level, it's all about repetition and precision, and Venus hadn't had that luxury.
It was Venus' first singles match for a staggering 485 days, since a Davis Cup tie with Korea in September 2018.
He hadn't won a tour-level singles match in more than 1000 days, in a Davis Cup against the same opponents in April 2017.
Despite that, the first set was a competitive affair.
Sandgren relied on his booming serve – which was a big part of his run to the title last year, while Venus also has a major weapon in that area.
But the Kiwi was under pressure in his second service game, saving one break point before double-faulting on the next.
He responded well, breaking back in the next game after a strong return forced an error from the Tennessee native.
Games then went with serve, until 4-5, with Venus' radar, unfortunately, went astray.
A wild forehand gave Sandgren a set point at 30-40, and the 28-year-old converted in the next rally, after Venus screwed a crosscourt backhand wide.
The Venus serve wasn't firing, he only landed 51 per cent of his first attempts, while Sandgren was more solid, sending down seven aces as he only lost four points on his first serve across the set.
Venus missed two early break opportunities in the second set, before Sandgren got himself out of trouble with a 205km/h ace.
That was his chance, as Sandgren was ruthless from there.
In the fourth game the American won four straight points – from 15-40 down – to gain an opening in the second set that he was never going to relinquish.
Venus never stopped fighting, but the margins for error at this level are slight, and the disparity proved too much.
