Defending champion Coco Gauff then suffered an early shock, struggling with double faults in Sunday's round-robin opener as Jessica Pegula beat her 6-3 6-7 (4-7) 6-2 in Riyadh.
Sabalenka, who won the US Open this year, landed 11 aces and frustrated Paolini with powerful returns near the sidelines, with the Italian growing tired as the match progressed in the Saudi capital.
World No.1 Sabalenka has now won 60 matches on the tour this year.
"Doesn't matter the score, I always know I have to stay focused. If you give an opportunity she will take control of the game," Sabalenka said afterwards.
"I was focused, I was calm and it feels like everything was in control."
Four-time grand slam champion Sabalenka got her first break with a backhand across the court to go 2-0 up.
Paolini troubled the world No.1 with low shots down the middle as Sabalenka's awkward forehand returns hit the net twice, with the Italian getting a crucial break to reduce the Belarusian's lead to 4-3.
But Sabalenka, runner-up in 2022, broke again to go 5-3 up, before landing four aces in the next game to hold her serve and secure the set 6-3.
Sabalenka built up a 4-0 lead in the second set, which proved to be unassailable for two-time slam finalist Paolini, who suffered a fifth straight loss to the Belarusian.
Two-time slam winner Gauff committed 17 double faults and 45 forehand unforced errors on a bad day as she lost to Pegula in the second game of the Group Steffi Graf.
The match began with five straight breaks, until Pegula managed to hold her serve to go 4-2 up.Â
Gauff saved two set points, but her struggles with double faults in the final game sealed the first set for Pegula.
Third seed Gauff bounced back in the second set, landing five aces and forcing Pegula to stay near the baseline. Gauff broke early to build a 5-4 lead, but committed two double faults as Pegula got the break back to make it 5-5.
Gauff broke again to go 6-5 up and was serving for the set, but committed three straight double faults to lose the game. The 21-year-old finally secured the set in a tiebreak.
Pegula was better prepared for Gauff's pressure tactics in the third set, as the fifth seed found the perfect angle for a forehand return from the baseline to go 3-2 up with a break.
A struggling Gauff could not win another game, registering 75 unforced errors in the 112 points she lost in the match.
"Coco's a great champion, great competitor, good friend, so it's always tough playing her... I just tried my best today to execute where I could," Pegula said.
World No.2 Iga Swiatek will look for her second straight win in Group Serena Williams as she faces Elena Rybakina on Monday, while Amanda Anisimova takes on fellow American Madison Keys.
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