Electronic line calling systems were also affected by the power cut, the ATP said, while spectators shared pictures of dark hallways at the Manzanares Park Tennis Center.
The fifth seeded German did not let up and another break confirmed the win in two hours and 40 minutes.
'I wanted to fight until the last ball and that was the key.'
Rafael Nadal is no stranger to being out of action for months due to injuries taking a toll on his body but when the Spaniard pulled out from a virtual reality tennis match that would have been contested using a game console - it raised a few eyebrows. The claycourt king had been expected to take on gamer DjMariio as part of a virtual Madrid Open charity event - but ended up being a no show on Monday.
Spanish teenager Carlos Alcaraz won his second ATP Masters 1000 title at the Madrid Open after defeating defending champion Alexander Zverev 6-3, 6-1 in front of his home crowd on Sunday.
Jabeur advances to first WTA 100 final in Madrid in style.
Rafael Nadal will have his work cut out when play begins next week, not on the Caja Magica's three red dust courts, but on gaming consoles.
With professional tennis tours closed down until mid July at the earliest because of the coronavirus pandemic, an esports version of the claycourt event is being staged online. Nadal showed impressive fingerwork to beat young Canadian Denis Shapovalov in his opening round-robin match on a digital representation of the Spanish capital's Manolo Santana Stadium.