BERLIN, March 4 — Bayer Leverkusen tightened their grip at the top of the Bundesliga with a 2-0 victory over 10-man Cologne to pull 10 points clear of Bayern Munich.

Xabi Alonso’s side were handed the opportunity to stretch their lead over Bayern after the serial champions faltered again, only managing a 2-2 draw at Freiburg on Friday night.