United still trail their local rivals by eight points at the top of the Premier League table, but they will go into the derby at Old Trafford in good form having won their last four league games, including a thrilling 3-1 victory at top-four rivals Arsenal on Saturday.
City, meanwhile, will be bidding for a record-breaking 14th consecutive league victory and have won their last 20 games on the bounce across all competitions, but they have needed late goals in each of their last four games to maintain that streak.
"We are going to find our best moment very soon. We are second and chasing to be top of the table. It was a fantastic result [at Arsenal] with some great performances. David [de Gea] was amazing, and we were clinical in the first half, with two chances in the first 15 minutes and two goals," Herrera told United's official website.
"Jesse [Lingard] is on fire now, Paul [Pogba] as well, it's a pity he got a red card. Romelu [Lukaku] didn't score but he helped us a lot. The centre-backs - Victor [Lindelof] is in fantastic form right now. So we are optimistic of course.
"I'm not thinking about Sunday, now it's about CSKA. We are not qualified yet so we don't think about City yet."
United have won their last eight Premier League matches at home, including all seven so far this season.