Holders held at home by purposeful Porto

Manchester United's Champions League hopes were left hanging by a thread after Porto substitute Mariano grabbed a late equaliser in an entertaining 2-2 draw in their quarter-final, first leg on Tuesday. The European champions looked to have got out of jail at Old Trafford when their Argentina forward Carlos Tevez came off the bench to fire home an 85th minute strike from Wayne Rooney's clever back-heel to put the struggling hosts 2-1 ahead. GALLERY: Manchester United 2-2 Porto photos It appeared to have capped an unlikely comeback after Porto stunned the home fans by taking the lead inside four minutes. United defender Jonny Evans was at fault, sending a poor clearance straight to Cristian Rodriguez who ghosted round the Ireland international before curling a smart left-foot shot beyond Edwin van der Sar into the bottom corner. Few realised at the time but it was a sign of things to come with the visitors continuing to dominate a United side looking short of pace and laboured in midfield. WOEFUL PASS Lisandro could have doubled Porto's lead but saw his strike saved by Van der Sar before United were gifted an equaliser courtesy of Bruno Alves's woeful back pass. Rooney could hardly believe his luck as he beat Porto goalkeeper Helton with a calm finish after 15 minutes. Despite their setback Porto continued to threaten through the impressive Hulk and Rodriguez. Van der Sar denied both players with impressive saves while Lisandro saw his deflected shot tipped wide by the Dutchman as the visitors went in search of a deserved second goal. Hulk was denied a penalty in the 75th when he appeared to be tripped by Tevez before the United substitute converted Rooney's clever pass to hand the home side an undeserved lead. It lasted just four minutes before Lisandro's cross found the unmarked Mariano who beat the onrushing Van der Sar to give Porto a valuable second goal and the upper hand in the tie. United may have extended their record unbeaten Champions League run to 22 matches but Alex Ferguson's side have been left with a mountain to climb in next week's return leg. UNITED FANS! Check FourFourTwo.com’s ever-expanding interviews archive for more stuff to read: Web Exclusives Wayne Rooney, Peter Schmeichel, Carlos Tevez Q&A Wayne Rooney, Cristiano Ronaldo, Ruud Van Nistlerooy One on One David Beckham, George Best Ask A Silly Question Bryan Robson Boy's A Bit Special Danny Simpson Perfect XI Garth Crooks, Bryan Robson, Sir Bobby Charlton, Eric Cantona What Happened Next? David May, Norman Whiteside Sing When You’re Winning Dominic Monaghan, Ian Brown And Another Thing Being a Big Four fan Plus! Rate United players (and others) on Talentspotter