Brentford held Chelsea to a frustrating draw in a stale west London derby, which ended 0-0 at the Gtech Community Stadium.
The Blues failed to strengthen their grip on fourth place in the Premier League, handing Man City the opportunity to leapfrog them in the table if Pep Guardiola's side are victorious in today's Manchester derby.
Meanwhile, Brentford missed the chance to keep putting pressure on the European places, as they now sit eight points off Newcastle in seventh.
MATCH FACTS
Brentford (4-2-3-1): Flekken; Ajer (Kayode 83'), Collins, Van den Berg, Lewis-Potter; Norgaard, Yarmolyuk (Janelt 66'); Mbuemo, Damsgaard (Jensen 83'), Schade; Wissa
Subs unused: Valdimarsson (Gk), Mee, Pinnock, Henry, Maghoma, Konak
Goals: O'Brien (90+1')
Manager: Thomas Frank
Chelsea (3-2-4-1): Sanchez; Chalobah, Tosin, James (Cucurella 77'); Gusto, Caicedo; Madueke (Neto 59'), Fernandez, Dewsbury-Hall (Palmer 59'), Sancho; Nkunku (Jackson 46')
Subs unused: Jorgensen (Gk), Badiashile, Acheampong, Colwill, George
Goal: Soucek (67')
Manager: Enzo Maresca
Referee: Michael Oliver