The Gunners lost 1-0 in the Champions League group stages to Italian champions Inter Milan.
Despite the loss, the Gunners are still in a position to qualify for the next round.
“It’s very tough,” Timber stated after the 1-0 loss away from home.
“Very frustrating for us. I think we played a good game, we dominated a lot but we didn’t score. In the Champions League, you have to score if you want to win. It’s a tough away game and small moments can decide a game.”
He added: “At the end, we felt confident, we had a couple of tough matches.
“On Sunday (Chelsea in the Premier League) will be tough again but I believe in our squad, we have a lot of quality, just need a little bit of luck in scoring more goals. Like I said, I have a lot of trust in our team and we’ll be fine for sure.”