Ricardo Quaresma helped the home side to a half-time lead in an evenly-balanced encounter, before Varela doubled Porto's advantage after the break. However a wonderful Joselu strike and an own goal by Alex Sandro ensured Frankfurt deservedly came back from the brink.
Quaresma breaks deadlock
Hoping to bounce back from defeats to Borussia Dortmund both in the Bundesliga as well as in the DFB Cup, Frankfurt began promisingly, enjoying more of the possession, though Porto looked the more threatening side. Striker Jackson Martinez looked particularly dangerous in the opening stages, heading the ball wide before giving Kevin Trapp in the Eintracht goal a first serious test with a shot from inside the area after 17 minutes.
Frankfurt appeared unruffled by Porto's advances and came close to taking the lead themselves near the half-hour mark when Sebastian Rode picked up Johannes Flum's throughball to break into the box, only for his effort to be denied by goalkeeper Helton. Armin Veh's men were punished shortly before the interval, however, when Quaresma's swerving long-range stunner found the back of the net.
Joselu sparks Frankfurt's fightback
The Hessians emerged for the second half in high spirits, bossing the game and carving out several goalscoring opportunities. Both Joselu and Marco Russ had powerful headers denied by Helton, before Trapp did well to keep Martinez's headed effort out at the other end. Varela extended Porto's lead a little later though, slotting in Maicon's cross from the edge of the six-yard box.
Eintracht were never going to give in though, and eventually saw their efforts pay off when Joselu's 25-yard rocket nestled into the bottom left corner. The visitors' pressure took its toll four minutes later as Sandro failed to clear Russ' header from a corner and only managed to steer the ball into his own goal off the crossbar. That sparked frantic Porto attacks in search of a late winner, but their efforts came to no avail, leaving the tie evenly balanced ahead of the return fixture next week.
Porto: Helton - Danilo, Maicon, Mangala, Sandro - Fernando, Josue (68' Carlos Eduardo), Herrera - Varela, Quaresma - Martinez
Frankfurt: Trapp - Jung, Zambrano, Madlung, Oczipka - Rode (72' Barnetta), Schwegler, Russ - Flum, Meier, Aigner – Kadlec
Goals: 1-0 Quaresma (44'), 2-0 Varela (68'), 2-1 Joselu (72'), 2-2 Sandro (77' own goal)