Arsenal moved on to 67 points with seven matches to play to lead the standings for the first time since January and keep the pressure on Manchester United and Chelsea, who play their weekend matches on Sunday.
United, who host Liverpool at Old Trafford, have 66 points from 30 games, followed by Chelsea who have 64 points from 29 and visit Blackburn Rovers.
They are followed by Liverpool (51 points), Manchester City (50) and Aston Villa (50), who were held to a 2-2 draw by Wolverhampton Wanderers in Saturday's early kick-off.
But the decision was a harsh one after West Ham's Mexico striker Guillermo Franco went down somewhat easily under the Belgian international's challenge in the box.
The defeat, West Ham's fourth straight league loss, left them in 17th place just three points above the relegation zone.
Fabregas told ESPN it was unfortunate Vermaelen would now be banned but added: "We don't want to make any excuses, we want to go all the way to the title and prove we can do it".
West Ham manager Gianfranco Zola said: "In the first half we played the best we've played all season and certainly deserved something more but in the second half, although we had the extra man we lost a bit of discipline.
"I'm disappointed because it was a big opportunity for us."
Earlier, Arsenal's north London rivals Spurs edged closer to a possible Champions League place after their victory at Stoke.
