The La Liga club trail 1-0 in their tie with the Portuguese powerhouses, ahead of their quarter-final second leg at the Estadio Ramon Sanchez Pizjuan.
Emery said he has fresh material to use for motivating his players, after some inspiring comeback efforts in the UEFA Champions League on Tuesday.
"We'll have to take care that they don't score against us and that we're closer to scoring goals ourselves, but we have to be prepared for if they score, whether it's early or late in the game," Emery said.
"We have to be patient.
"Yesterday there were two good examples with Borussia Dortmund and Chelsea, we should have a similar response.
"We have to make it a long game for our opponents, because that will give us more options."
Dortmund fell one goal short of forcing extra-time in their tie with Real Madrid, despite trailing 3-0 after the first leg, while Chelsea arrested a two-goal deficit to progress to the last four past PSG.
Sevilla will benefit from the absence of Jackson Martinez and Fernando for the visitors, although Emery said Porto's depth will be capable of covering the hole left by the midfielder and attacker.
"They're not going to have those two available, but they'll have another two playing and a strong 11," Emery said.
"If you're playing at Porto, it's because you're a good enough footballer.
"I'm not evaluating Porto based on any of their absences, but rather that they'll have two different players involved."
Emery is so focssed on the European fixture, their derby with Real Betis in the league on Sunday - which could see them put their rivals on the brink of relegation - was not on his radar.
"What derby? All our enthusiasm and focus is on the game tomorrow," Emery said.
"We have to make a big effort together, to enjoy this moment and make the most of it.
"That's the enthusiasm we have to convey, to create a positive atmosphere, that we feel the support of our 12th man in the crowd."
