The defending champions Manchester United were held to a shock 2-all draw by Porto at Old Trafford to leave their Champions League quarter-final on a knife-edge ahead of the second leg in Portugal next week.
United extended their record unbeaten run in the competition to 22 matches but failed to gain the advantage they wanted from an open and entertaining match.
The match was locked at one-one at half time, before both teams scored in the dying minutes with Carlos Tevez putting United 2-1 up after 85 minutes and Mariano equalising for Porto in the 89th.
In the mornings other match, a 66th minute equaliser from Emmanuel Adebayor gave 2006 finalists Arsenal a crucial away goal in a 1-all draw with Villareal.
