Chelsea interim boss Guus Hiddink believes John Obi Mikel's away goal in the 2-1 defeat at Paris St Germain could be key in determining the victor of the last-16 tie.
A rare goal from Mikel cancelled out Zlatan Ibrahimovic's opener before substitute Edinson Cavani earned a 2-1 first-leg win for the hosts at the Parc des Princes.
Away goals have separated these sides in the Champions League in each of the last two seasons and Hiddink is optimistic Chelsea's position is favourable ahead of the March 9 second leg at Stamford Bridge.
"I'm never happy with a loss but it's not a dramatic loss," said Hiddink, who saw his 11-game unbeaten run end.
"I think it's 50-50 still. You have to consider it's a two-leg game. Scoring away is always good."
Gary Cahill told BT Sport: "It's poised now, we know what we have to do and we have done it before at home. We go all in now."
Hiddink expressed jealousy at the options at Laurent Blanc's disposal after Cavani's impact.
"I envy a bit the bench of PSG. They have a very strong bench," Hiddink said.
Chelsea's defensive effort was impressive, but Eden Hazard made a limited impact.
The Belgium playmaker, who chose the eve of the match to reveal it would be difficult to turn down a move to PSG, did little to boost any potential transfer fee and was withdrawn 19 minutes from the end.
Hiddink said: "He had a threat forward and he had some good runs, but of course this was a game with a high intensity. After 65, 70 minutes it was enough for him.
"He has to grow and when he does, his shape will grow as well.
"Happily we also have Oscar for his position. He will be better and better."
PSG took the lead when Mikel fouled Lucas Moura and Ibrahimovic's resulting free-kick deflected off the Nigerian.
Diego Costa had earlier had a header tipped on to the bar by Kevin Trapp and Hiddink rued further missed opportunities.
"We could have been a little bit more lethal in the four, five counters we made," he added.
John Terry missed the trip to Paris and may have to wait for his 700th Chelsea appearance as he is a doubt for Sunday's FA Cup fifth-round tie with Manchester City.
Hiddink will not rush the captain back.
"We'll see," he added.
"We must be careful. We must not go into a situation where he will drop back into a longer period of injury."
Cahill and Branislav Ivanovic stepped up in the absence of Terry and Kurt Zouma, who is out for the season with a knee injury.
"The players did well, not just the four defenders," Hiddink said.
Blanc rued the concession of an away goal and said PSG would strive to score at least one of their own in London in three weeks' time.
"When you play at home you need to be stronger in defence because, if you concede a goal, it effectively counts double," Blanc said.
"Chelsea scored, so we go to Stamford Bridge eager to score ourselves.
"We'll have chances, most likely, so it'll be about defending well but we are an attacking team.
"We have chances to score there. I hope we do."
Blanc predicts an open second leg.
He added: "I don't think Chelsea will change their approach for the second leg. Neither will we.
"So the return game will probably be open and, hopefully, with some goals."