Substitute Leonardo struck with 13 minutes to go to secure three points for AFC Ajax as Hamburger SV were made to pay for a loose back-pass in Group F.
The 25-year-old chased a misplaced defensive ball from home captain David Jarolím and then rounded goalkeeper Frank Rost to score. However, there were a few hearts in mouths on the Ajax bench as the Brazilian's initial shot hit both posts before Leonardo stole in to finish at the second attempt and seal a second 1-0 win for his side in as many visits to Hamburg.
Luis Suárez seized the first chance of the game for Ajax, pouncing on a ball from a header but seeing his shot deflected wide at the last moment. Hamburg's main attacking threat came down the left and Ivica Olić danced his way past two defenders along the touchline before forcing a save from Ajax keeper Kenneth Vermeer with a shot from a tight angle. The Croatia striker then cut in from the right side and unleashed a left-footed strike which went just inches past the far left post in the 28th minute. Hamburg keeper Frank Rost, though, needed to be on his guard to cut out Suárez's through-ball in first-half injury time.
Ajax started the second half brightly, but the hosts remained resilient at the back, and should have taken the lead on 59 minutes with Paolo Guerrero crashing a shot against the bar as the guests struggled to clear their lines. Hamburg boss Martin Jol brought on Mladen Petrić for Guerrero with 15 minutes to go to try and win the game, but it was Ajax substitute Leonardo who stole the show. Rost then stopped Ajax from moving further ahead four minutes later with a save from Urby Emanuelson.