Porto face must-win showdown with Zenit
Porto are third in Group G with seven points behind Russian league leaders Zenit who have eight and need only a draw to reach the last 16. APOEL Nicosia have nine points and have already become the first team from Cyprus to get to the knockout stage.
Porto won the domestic double and Europa League last season with a rampant attacking style of play but have been disappointing so far this term after Andre Villas-Boas left for Chelsea and his assistant Pereira was promoted to manager.
In the Champions League, Porto started with a win over visiting Shakhtar Donetsk but lost at Zenit, were held at home by APOEL and then suffered a shock defeat in Nicosia that triggered a chorus of protests that included dozens of fans waiting at the airport to berate the returning players and coach.
To make matters worse, they were soon knocked out of the Portuguese Cup, outplayed in a 3-0 defeat at Academica.
Under intense pressure, Pereira then changed tactics and his side earned two straight wins with a gritty 2-0 victory in freezing conditions at Shakhtar and a 3-2 home success against Braga in the league.
"Unfortunately things were not coming out well for us. Now the team has improved and wants to keep the momentum, beat Zenit and move ahead in the Champions League," said Porto's Brazil forward Hulk.
Pereira shifted to a 4-2-3-1 formation from 4-3-3, making the midfield more dynamic as he dropped one of the three holding midfielders and moved Hulk from the wing to spearhead the attack.
The burly forward has hit his stride in the new role, scoring three goals in the last two matches and driving the team's attack.
"Positive results always bring confidence... I'm no exception to that rule," Pereira said. "But I'm not calm yet and will not lower my guard, although I feel that the team is closer to what we are looking for," he said.
In midfield, steady passer Joao Moutinho has recovered form while energetic Belgian Steven Defour offers more pace than Fernando Belluschi, an Argentine playmaker who prefers possession football.
Russian champions Zenit will be without leading scorer Alexander Kerzhakov, who has stayed home to nurse an ankle injury.
Luciano Spalletti's team will make the short trip to Porto on Monday having opted to fly to Portugal last week for a six-day training camp.
Porto: 1-Helton; 4-Maicon, 14-Rolando, 30-Nicolas Otamendi, 5-Alvaro Pereira; 28-Fernando, 8-Joao Moutinho, 20-Djalma, 35-Steven Defour, 19-James Rodriguez; 12-Hulk.
Zenit St Petersburg: 16-Vyacheslav Malafeyev; 2-Alexander Anyukov, 4-Domenico Criscito, 6-Nicolas Lombaerts, 14-Tomas Hubocan; 15-Roman Shirokov, 20-Viktor Faizulin, 18-Konstantin Zyryanov, 27-Igor Denisov; 10-Danny, 9-Alexander Bukharov.