With five matches remaining, Ajax are top with 63 points, three ahead of PSV Eindhoven and Vitesse Arnhem, who had wins over Willem II Tilburg and NAC Breda respectively on Saturday.
Feyenoord are fourth with 59 points following a 1-0 home win over lowly VVV Venlo on Friday.
Dane Lasse Schone opened the scoring for Ajax after 13 minutes when he broke through the Almelo defence after a combination with Kolbeinn Sigthorsson.
Three minutes into the second half Ajax were reduced to 10 men when Vermeer was sent off for a foul on Geoffrey Castillion. He will miss next week's clash with PSV Eindhoven.
Ajax adapted quickly and doubled the lead through Sigthorsson who hit the bar before netting a rebound.
Ryan Babel and Christian Eriksen scored in the final 15 minutes to complete the rout.
"I went for the ball but missed it and hit Castillion so that was clear," said Vermeer. "I'm bitter that I will miss the match against PSV but confident that Jasper [Cillessen] will replace me well like he did today."
Sixth-placed Utrecht, on 51 points, closed in on a Europa League play-off ticket as they beat ADO Den Haag 1-0 thanks to former ADO player Jens Toornstra who scored from close range.
Groningen had a 3-1 win over Heerenveen in the northern derby after a third-minute own goal from Jukka Raitala and a converted penalty from Leandro Bacuna gave them a two-goal lead at half-time.
Lucas Marecek pulled one back for the visitors 20 minutes before time but a bicycle kick from Michael de Leeuw in the 87th minute sealed the result, ending a five-match winning streak by Marco van Basten's men.
