Spaniard Sainz was fastest overall on Friday, delighting the home crowd at Monza's famed "Temple of Speed", and again set the pace in the final session before qualifying with a best lap of one minute 20.912 seconds.
Verstappen was second fastest, 0.86 slower, with Mercedes' Lewis Hamilton third but more than half a second off the Ferrari's pace.
Sainz was shown a black and white flag for impeding McLaren's Oscar Piastri, however.
Ferrari's Charles Leclerc, who started on pole last year in a race won by Verstappen, was fourth fastest with Aston Martin's Fernando Alonso fifth and Mercedes' George Russell sixth.
Verstappen's Mexican team mate and closest rival Sergio Perez, was only 10th and ended the session early with mechanics working on his car. The Mexican is 138 points behind Verstappen after 13 of 22 races in a season dominated by Red Bull who have won every race and the last 14 in total.
McLaren's Lando Norris was only 17th and complained during the session that he had to go off track to avoid the Alfa Romeo of Guanyu Zhou.
"Why are people so stupid?" he asked over the radio. "Why can't they look in the mirrors?"
Zhou was also shown a black and white flag.
