Pep Guardiola decided against bringing on more than one substitute during Manchester City's goalless draw at Old Trafford because he felt his players were "sharp".
The City boss has been a strong advocate of the Premier League bringing in five substitutions this season but he's now only used five replacements in the last four games, two of which very injury-enforced.
Against United he only bought Ferran Torres on for Riyad Mahrez with 24 minutes remaining, ignoring the claims of Phil Foden and Bernardo Silva, among others, in what proved to be anticlimatic derby.
Guardiola didn't make any substitutes in the win over Fulham last weekend, leading to some suggestions he was making a point, but he's continued to keep changes to a minimum this week and explained his thinking after the derby stalemate.
"My decision. I saw the team and the players there looked sharp. Kevin, Gaby, we had chances. It was my decision," he said.
"The rules are the rules and I have to use the rules. Maybe next game we’ll do three, maybe in the Champions League maybe we'll five. I have the rules and I use the rules as I want.
"It would be better to have five subs, it would be better to have more players on the bench, but as a manager it's your decision whether to use it or not."
Guardiola admitted his team again failed to take their chances, but he was delighted with a six successive clean sheet.
"We struggle to score goals so we have to be solid in controlling the game. I’m so proud, when you let this team run they kill you, we did it perfectly," he said.
"The offside penalty, it happened quite often, they beat you because they’re so strong and so fast, in the set pieces they are better than every other team in the Premier League.
"Coming here to Old Trafford and playing the game like that is quite good. I know the expectation is always so high, we accept this."
