Porto, Portugal:Andriy Shevchenko scored in the 16th minute on Wednesday to help Chelsea rally from a goal down and draw 1-1 at FC Porto in the first leg of the second round of the Champions League. Chelsea lost central defender John Terry to an injury in the opening stages and his departure immediately changed the complexion of the game. Chelsea had only 10 men on the field when Raul Meireles put the hosts ahead in the 12th with a volley from the edge of the area that ricocheted off Frank Lampard and bounced past goalkeeper Petr Cech. But then Chelsea manager Jose Mourinho, playing against the club he led to the 2004 Champions League title, brought on Arjen Robben for Terry and dropped Michael Essien into the back line. Four minutes later, Robben set up Shevchenko to hit a low drive into the corner. Terry crawled off the field in the eighth minute after apparently twisting his right ankle, putting him in doubt for Chelsea's League Cup final against Arsenal on Sunday. A sloppy clearance by Claude Makelele allowed Meireles space for the opening goal. Mourinho appeared angry at John Obi Mikel, the defender initially sent to warm up as a replacement for Terry. Obi Mikel seemed to take too long to remove his tracksuit. Instead, Mourinho sent on Robben, who immediately found space down the left flank against a team that had kept a tight defense. He cut inside from the wing and laid off the ball for Shevchenko. But Robben went off injured at the interval. "I'm satisfied with the result," Mourinho said. "We had to cope with a series of setbacks. "We didn't have any central defender on the subs' bench. ... I'm worried about these injuries that keep occurring." Porto coach Jesualdo Ferreira said Robben's entrance was the difference. It "knocked us off balance. We weren't expecting it and we didn't react well," Ferreira said. "We played very well in the first half and at the beginning of the second, but Chelsea's experience and our nervousness made us lose our calm going forward." No flow Chelsea had trouble finding fluency against the Portuguese champions, and Lampard and Michael Ballack rarely found space to sparkle in midfield. Meanwhile, Porto kept pushing forward and could have gone back into the lead. Lisandro Lopez got behind the Chelsea defense but sent his shot at Cech, and Ricardo Quaresma hot a curling shot against the crossbar. Mourinho replaced Robben with Obi Mikel at halftime. Chelsea suddenly appeared tame again while Porto took the initiative. Porto pressed forward but lacked clarity in attack, and Adriano replaced striker Helder Postiga with 15 minutes left. Chelsea was mostly content to weather the pressure and hope to ensure it qualifies for the next round in the return leg. Didier Drogba hit the post from a tight angle and Lampard tested goalkeeper Helton with a long-range effort in the closing stages but the English champions rarely looked likely to dominate.