City continued their high-scoring ways at the Etihad Stadium, taking their goal tally to a remarkable 35 goals in eight matches at home.
While Argentina striker Sergio Aguero, who limped out of the match early in the second half with a calf injury, and Alvaro Negredo have gained many of the plaudits this season, Fernandinho, signed from Ukrainian side Shakhtar Donetsk in June for a reported 30 million pound ($48.83 million) fee, has been one of City's quiet achievers, starting 13 matches for the 2011-12 champions.
The Brazilian capped another strong performance with his first league goals for City. He followed up a curling effort early in the second half with a deft chip over Arsenal goalkeeper Wojciech Szczesny after a fast break involving Samir Nasri.
"Fernandinho played a perfect game in all senses, not just his two goals but he recovered a lot of balls and had a lot of pace," Pellegrini told reporters.
"I am very happy for him but you will see how good he is over the season - he will get better every week.
"Yaya (Toure), Samir and David (Silva) all played very well today, too. The four in the midfield are very difficult to play against - the strikers can score a lot of goals with them behind them.
"He (Fernandinho) is a typical Brazilian midfielder, he plays very well with the ball, he has a lot of pace - he gets forward well. He's doing very good work with Yaya Toure and I'm very happy for him."
Capped five times by Brazil, but only an outside chance of making the side for the 2014 World Cup, Pellegrini said the midfielder was showing why he was worth splashing such a high transfer fee on.
"Important players aren't cheap."
($1 = 0.6143 British pounds)
- Sports & Recreation
- Sergio Aguero
- Alvaro Negredo
- Shakhtar Donetsk