Torres profited from a mix-up between Matija Nastasic and England goalkeeper Hart to net the winner in Chelsea's 2-1 defeat of City on Sunday.
Nastasic headed a long punt down field from Willian back towards Hart, who had already raced to the edge of his area, and Torres exploited the mistake to score his first Barclays Premier League goal of the season.
"He (Torres) never gives up," Cech told Chelsea TV.
"This is why he scored the second goal, because he was chasing the guy all the way and the defender (Nastasic) made a mistake.
"He didn't see the goalkeeper (Hart) coming, which I thought he had plenty of time to see the goalkeeper coming, but he didn't because Fernando was putting him under pressure.
"And because he (Torres) followed he had an easy tap in."
Torres' performance against City, following on from his two goals at Schalke, led many to suggest the World Cup-winning striker is back on top form.
The 29-year-old's performances have been scrutinised since his £50million move from Liverpool, particularly due to his perceived lack of goals, but Cech insists his contribution has always been valuable, even when he has not been scoring.
"This is the debate everybody's been having for a long time," Cech added.
"There were so many games when Fernando was absolutely brilliant, but because he didn't score everybody's saying 'oh, he didn't score'.
"Now he's scoring goals, he's making goals, he's playing as well as he has during his life."