City finished third in their Champions League group behind Bayern Munich and Napoli, and Roberto Mancini’s side lost at the Allianz Arena and Stadio San Paolo on their travels.
Milner has called on the Eastlands outfit to improve their away performances and show togetherness against the Europa League holders in the first leg of their last-32 tie.
“It’s important to have a good team spirit in the squad, and throughout the season we have had that,” Milner told City’s website. “You are going to face tough teams in tough spots, you might go down to 10 men and be under pressure.
“That’s when you need everyone to pull together and show that team spirit.
“We’re going well in the league and we have to keep pushing forward, but when things are not going right then togetherness and team spirit can get you what you need.”
Porto are unbeaten in seven European home games – five wins and two draws – since a 1-0 defeat by Sevilla in last season’s last-32 second leg.
Chelsea manager André Villas-Boas led the Portuguese side to the Europa League title, beating Braga at the Aviva Stadium in Dublin last May – and current Porto boss Vítor Pereira considers his side as one of the favourites to retain the title.
“Everyone knows about City’s strength, they are the leaders in the Premier League,” said Pereira.
“They have a great team, but I am focused on the quality of our game. At our best level, we have more than enough to win the game. Porto are clearly one of the favourites to win the Europa League.”
• Porto have hosted City’s neighbours Manchester United four times, recording two wins, a draw and a defeat. At Old Trafford they drew 1-1 in 2003-04 and 2-2 in 2008-09, losing in 1977 and 1997. Their 10 other visits to England have all also ended in defeat.
• City’s only previous meeting with Portuguese opponents came in the quarter-finals of their triumphant 1969-70 Cup Winners’ Cup campaign, when they drew 0-0 at Académica de Coimbra before Tony Towers scored the only goal of the tie in the 119th-minute at Maine Road.
• Porto’s two most recent Uefa Cup and Europa League campaigns, in 2002-03 and last season, ended with them winning the tournament. And they have not lost a two-legged tie since a 2-0 aggregate defeat by Liverpool in the 2000/01 quarter-final.
• Mancini’s men have won only one of their last seven European away games, a 3-0 victory at Villarreal in this season’s Champions League group stage in a run of two draws and four defeats.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news