Watch as Webo's boot flies up to meet Koscielny high up the right-hand side of his cheek. The challenge, deemed a dangerous play, yielded a yellow card.
It left Koscielny shaken and needing to be substituted.
Arsene Wenger's men came desperate to avoid a potentially devastating defeat in the first leg of their Champions League qualifying playoff.
They ended up with a hugely important 3-0 victory.