Arteta has rued missed chances against Jindřich Trpišovský’s men, leaving the Gunners with a tough mountain to climb in order to reach the next stage of the competition.
After a goalless first half where Arsenal passed up glorious chances to take the lead, Nicolas Pepe broke the deadlock four minutes before the final whistle after he was teed up by substitute Pierre-Emerick Aubameyang.
Arsenal thought they had secured a crucial victory going into the second leg in the Czech Republic capital but Tomas Holes popped up to pull parity for the visitors with a header.
"It's difficult because they were a good opponent. They have beaten some big teams and are really difficult to play against,” Arteta said after the game.
“They have a lot of man-to-man situations and you have to resolve them. When we did that, we created chances, but when you can't, it's not easy.
"We were effective in our high press - they had the capacity to run in transition if they won the ball back but we controlled that well. It's more about the final result that leaves a difficult taste."
The Spanish coach said his side must put up a stellar performance to beat Slavia Prague next week.
He added: "We need to win the game. The mindset is to win the game, we need to score, we've done it before and we need to do it again."
