The Gunners' 18-match unbeaten run in all competitions ended at Villa Park when Emiliano Buendia struck with virtually the final kick of the game to seal a dramatic 2-1 win for Villa. It proved a costly afternoon for Mikel Arteta's side, as their lead at the top of the table was cut to just two points after Manchester City defeated Sunderland.
Timber, who was forced to play out of position at centre-back due to an injury crisis, said the squad needed to respond in the right way.
"I think in the end you need to use it as a motivation and in the end as a strength, because it happened and we need to accept it and we need to get better," Timber said.
"At the same time, within the season, I think these moments happen, set-backs, and you just have to step up after that."
Normally deployed at right-back, Timber filled in centrally with William Saliba and Gabriel both unavailable, while Cristhian Mosquera has also been ruled out for weeks with an ankle problem. Timber admitted the defensive injury list has disrupted Arsenal's rhythm.
"Yes, it is a disruption," he said. "I think we have a great squad. Players that come in always do really good, but obviously it's not always easy. We can't play every week with the same players. But it's part of the season.
"It happens at every club and with us it's the same and we just have to manage that and win our games."
Villa's victory underlined their growing title credentials, moving them to within three points of Arsenal. Unai Emery's side have been in outstanding form, winning nine of their last 10 Premier League matches.
Matty Cash gave Villa the lead before Leandro Trossard levelled early in the second half. Buendia's late winner sparked wild celebrations inside Villa Park on Saturday.
Arsenal's upcoming matches in December are against - Club Brugge, Wolves, Everton, Crystal Palace, Brighton, and Aston Villa across the Champions League, Premier League, and EFL Cup.
Xabi Alonso has demanded an immediate response from Real Madrid after they were stunned at home by Celta Vigo, admitting his side were "angry" and determined to put things right when they face Manchester City in the Champions League.
Rasmus Hojlund powered Napoli to the top of Serie A after scoring twice in a dramatic 2-1 win over Juventus, ending his eight-game goal drought in emphatic style.
Liverpool have faced another difficult week after a dramatic 3-3 draw with Leeds United at Elland Road, where Ao Tanaka scored a last-gasp equaliser in stoppage time.
Crystal Palace striker Eddie Nketiah was delighted to be back on the pitch and celebrated his return with a goal against Fulham in the Premier League.
