The Gunners striker is in outstanding form having scored 14 goals in his last 11 appearances. That run has propelled the north London club up the Premier League table and they head to the Etihad Stadium to face the leaders having won seven in eight games. City boss Mancini said: "We know that every game we could meet a top striker. "In the last game we met (Didier) Drogba, and on Sunday Van Persie. "We must work harder when you play against a top team with a top striker. "Van Persie is an incredible player. "At this moment he is very good, like Arsenal. At this moment they are playing very well." City are looking to get back to winning ways after surrendering their unbeaten record in a 2-1 loss at Chelsea on Monday. And for all their brilliance this season, they could even be second in the table come kick-off if Manchester United beat QPR earlier in the day. Mancini said: "At the moment, us, United and maybe Tottenham are the three teams that can fight for the title. "But the season is long. Chelsea, Arsenal and, maybe, Liverpool could also try. "The season is hard. We have a lot of games to play in the next 40 days." City swooped on Arsenal to sign one of their stars of last season, Samir Nasri, in August. But the Frenchman has failed to command a regular starting spot in City's impressive side since his £24million switch from the Emirates Stadium. The 24-year-old showed glimpses of his talent as he started four successive games recently but he was back on the bench at Stamford Bridge and Mancini is demanding more from him. Mancini said: "In my opinion Nasri is a champion - a top, top player. "I think he can do more but when you change teams you can have a problem. "At this moment his confidence is maybe not very good because he didn't play against Chelsea but if he plays Sunday he has a chance to show us. "I would like Nasri to play better, because he is a really good player." Mancini feels now would be a good time for Nasri to step up with midfield linchpin Yaya Toure heading off to play in the African Nations Cup in January. The Italian said: "We will lose an important player but I hope Samir can play more games at a higher level. "He is a top player. Every game a player like that should contribute."