The teams were drawn into twelve groups of four, and played each other home-and-away in a round-robin format. The top two teams in each group advanced to the round of 32, where they were joined by the eight third-placed teams from the Champions League group stage.[2]
Each group contained one team from each of the four pots, with the restriction that teams from the same national association cannot be drawn against each other. Moreover, the draw was controlled for teams from the same association in order to split the teams evenly into the two sets of groups (A–F, G–L) for maximum television coverage.
The fixtures were decided after the draw. On each matchday, six groups played their matches at 19:00 CET/CEST, while the other six groups played their matches at 21:05 CET/CEST, with the two sets of groups (A–F, G–L) alternating between each matchday. There were other restrictions, e.g., teams from the same city in general did not play at home on the same matchday (UEFA tries to avoid teams from the same city playing at home on the same day or on consecutive days), and Russian teams did not play at home on the last matchday due to cold weather.
Tiebreakers
The teams are ranked according to points (3 points for a win, 1 point for a tie, 0 points for a loss). If two or more teams are equal on points on completion of the group matches, the following criteria are applied to determine the rankings:[2]
higher number of points obtained in the group matches played among the teams in question;
superior goal difference from the group matches played among the teams in question;
higher number of goals scored in the group matches played among the teams in question;
If, after applying criteria 1) to 4) to several teams, two teams still have an equal ranking, criteria 1) to 4) are reapplied exclusively to the matches between the two teams in question to determine their final rankings. If this procedure does not lead to a decision, criteria 6) to 8) apply;
superior goal difference from all group matches played;
higher number of goals scored from all group matches played;
higher number of coefficient points accumulated by the club in question, as well as its association, over the previous five seasons.
Groups
The matchdays were 20 September, 4 October, 25 October, 8 November, 22 November, and 6 December 2012.[4]
Times up to 27 October 2012 (matchdays 1–3) are CEST (UTC+2), thereafter (matchdays 4–6) times are CET (UTC+1).
Note 3: The Sporting CP v Videoton match, originally scheduled to take place on 6 December 2012, 21:05 CET, was postponed due to a waterlogged pitch.[59] It was rescheduled to take place on 7 December 2012, 21:05 CET.
Note 6: The Ironi Kiryat Shmona v Athletic Bilbao match, originally scheduled to take place on 22 November 2012, 19:00 CET, was postponed by UEFA on 21 November due to the ongoing security situation in Israel.[73] It was rescheduled to take place on 28 November 2012, 19:00 CET.[74]
Note 8: The Rapid Wien v Rosenborg match was played behind closed doors due to the punishment handed to Rapid Wien by UEFA following incidents at their play-off round first leg against PAOK on 23 August 2012.[90]
^"First win in Europa League". Borussia Mönchengladbach official website. 25 October 2012. Archived from the original on February 10, 2013. Retrieved 26 October 2012.
^Rose, Gary (8 November 2012). "Bordeuax 1-0 Marítimo". Girondins.com. Girondins.com. Archived from the original on 3 February 2013. Retrieved 8 November 2012.
^Rose, Gary (22 November 2012). "Newcastle United 1–1 Marítimo". BBC Sport. British Broadcasting Corporation. Retrieved 23 November 2012.
^"Stuttgart 0–0 Copenhagen". VfB Stuttgart official website (in German). 25 October 2012. Archived from the original on 3 March 2016. Retrieved 25 October 2012.
^Skogli, Chris Thomas (25 October 2012). "Metalist snudde kampen". Rosenborg B.K. official website (in Norwegian). Archived from the original on 27 October 2012. Retrieved 25 October 2012.
^"Helsingborg 2–2 Twente". Helsingborgs IF official website (in Swedish). 4 October 2012. Archived from the original on 18 April 2013. Retrieved 5 October 2012.
Note: Between the 1999–2000 and 2008–09 seasons, the competition was still known as the UEFA Cup. All seasons are included following the competition's absorption of the Cup Winners' Cup.