Andriy Shevchenko's 58th European goal could prove vital to Chelsea's continued progress in the Champions League but they were left with a major concern over the fitness of John Terry ahead of Sunday's Carling Cup final.

Terry was stretchered off in the first half with an ankle ligament injury that will make him a major doubt for Sunday's showdown with Arsenal at Cardiff.

The England captain has only just returned to first team action after undergoing back surgery in December and having his comeback delayed by a calf injury.

Porto took full advantage of Terry's absence by scoring their 11th minute opener while the England skipper was receiving treatment on the sidelines, Raul Meireles despatching a volley into the far corner of the net from 20 yards.

Chelsea sent on Dutch winger Arjen Robben in place of Terry and his clever pass put Shevchenko in the clear. The Ukraine striker, the second highest European goalscorer of all time, coolly slotted the ball into the corner for the leveller.

The game required a spark to lift it but Chelsea were content to weather what little Porto had left in the tank.