Champions Arsenal needed an 80th-minute goal from Noni Madueke, their only shot on target, to scrape a 1-0 win at Nottingham Forest on Sunday and remain three points behind Premier League leaders Manchester City.
Ibrahim Sangare hesitated when he could have cleared the ball, leaving Forest manager Oliver Glasner visibly fuming, and second-half substitute Madueke then danced past Daniel Munoz before hammering a shot that deflected off Jair Cunha and wrong-footed Matz Sels.
"We're really happy, we did it all together. We showed grit, determination, and maybe we showed a champion spirit here for that, really pleased," Madueke told Sky Sports.
Murillo almost salvaged a point for Forest in injury time when he beat three players before unleashing a shot that sailed agonisingly wide.
The defeat left Forest, who have yet to win or even score at the City Ground this season, in the drop zone in 18th place with five points.

Gomez stunner highlights Brighton rout of Palace, Man United held by Leeds
Davidovich Fokina overcomes Jodar to claim Shanghai Masters crown
Chwalinska outwits Brit Kartal to win Wuhan Open
Chelsea's Martinez undergoes surgery after collision at Everton
Dubois defeats Wardley in short order to retain WBO heavyweight title