Arsenal held on to a 1-0 win against FC Zurich at the Emirates Stadium on Thursday to move through to the round of 16 in the Europa League Group A.
Mikel Arteta's team might have been pushed into the Europa League playoff round if they had placed second in their group behind PSV Eindhoven, who also overcame Bodo/Glimt to take all three points on Thursday, but they won the hard-fought encounter to top the group.
Kierney took advantage of a loose ball at the top of the penalty area to score the game's lone goal, slamming a first-time effort past Zurich keeper Yanick Brecher at his far post to give Mikel Arteta's team the lead after 20 minutes.
Arsenal controlled the first 45 minutes, outshooting Zurich 12-4 and spent the majority of the time in attack, but only had Tierney's goal to show for it as they went into half-time with a 1-0 advantage.
The hosts passed up multiple opportunities to increase their advantage and were nearly forced to pay.
When a goal-bound shot from teammate Fabio Vieira struck him a few yards away with Brecher beaten, Gabriel Jesus accidentally kept it out. Zurich had the ball in the net after a rare surge forward in the second half, but Adrian Guerrero was cautioned for offside, and they squandered a number of late chances to salvage a point.
The visitors frustrated Arsenal throughout the second half, setting up a tense end for the Gunners, with Zurich inches away from equalising in the 80th minute when Bohdan Viunnyk's rocket from distance barely missed the top-left corner.
Despite winning five of their six group games, PSV made it difficult for Arsenal to win the group, finishing second with 13 points and awaiting the results of Monday's draw to discover who they will meet in the playoff.
Arsenal will learn their round-of-16 opponent in the draw on February 24, following the conclusion of the playoff round matches between the eight Europa League second-place finishers and their Champions League third-place equivalents.