Koscielny believes Barcelona are the best team in Europe, but believes the Gunners can beat them.
"It’s a big game against the best team in Europe," said the French defender. "They’ve been at the top, at their best level now for quite a few years.
"I think a lot of players would dream of playing in that team. They’re always offering something, the way we like to see it, (football) played on the ground.
"They’re small in size, but know how to play with their feet and with their minds. It will be a hard game but you never know in football, there can be upsets.
"I watch their games from time to time on television, you often see them on the summaries on various programmes. Straight away you notice their quality in how they play.
"They’re a really collective team with really strong individuals."