Grealish enjoys his goal
Pep Guardiola was defending Jack Grealish again before this game, talking in his pre-match press conference of the dangers of measuring players solely in goals or assists.
There is value in that view - Bernardo Silva is one that makes the team better without necessarily making the key contributions - but however much the Manchester City manager may like it to be otherwise there is no denying how important such stats are to the players themselves.
Grealish has said himself he needs more goals and assists with his new club, and if he wants to stay in the team he will have to start producing them. Having not had it easy since leaving Aston Villa, you could see how much Grealish enjoyed his goal at Peterborough and the reaction of the players - starters and substitutes - was telling as they all went over to celebrate his first goal in two-and-a-half months.
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All hope there is much more to come, but there really is nothing like a goal to boost confidence - as shown when he nearly bagged another with a chipped effort late on.
Mahrez and Foden make their mark
With City struggling to test the Peterborough goalkeeper, Riyad Mahrez took him completely out of the equation as the hour-mark approached. Mahrez bamboozled his defender and shot through his legs, to give the stopper no chance and give City a lead they arguably hadn't earned.
One supreme assist from Phil Foden later, the tie was over and City had two high-quality goals to separate themselves from their opponents in a game where they had struggled to make the gulf in class tell. That is the benefit of having world-class players, and why Foden and Mahrez remain two of the biggest matchwinners Guardiola has at his disposal.
Fernandinho gesture shows his class
Fernandinho has been a terrific player for City and, despite playing fewer games in recent years, the 36-year-old has been a terrific captain. Nobody around the club has a bad word to say about the adopted Mancunian that came from Brazil via Ukraine in 2013, with hopes that he will extend his stay for yet another season.
Fernandinho was named captain against Peterborough but the 36-year-old chose to give the armband to Oleksandr Zinchenko in support of Ukraine and everything that the country and the individual has been going through. A classy gesture that underlines the top person as well as the top player.
Pitch not perfect
City will hope that this is the worst pitch they play on between now and the end of the season. There were sticky patches and there were bobbles and when a player with as good a first touch as Mahrez is struggling to control the football you know there must be something up.
That, of course, is one of the levellers that helps make the cup competitions special, with the Premier League team having to adapt to conditions that their opponents were familiar with. But the Blues will be grateful to get back to the bowling green at the Etihad in time for the derby.
Laporte passes minutes milestone
With Aymeric Laporte playing the second half of this match, the 45 minutes meant that the Spanish centre-back has already played more for City this season than he managed across the whole of the last campaign. That is a promising return, and a welcome return to form for a defender who really didn't enjoy spending so much time on the bench last year.
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