Chelsea had looked set to be knocked out of the competition by npower League One side Brentford, only for Fernando Torres to spare their blushes with an equaliser.
Elimination would have been unthinkable for the west London club, who were Capital One Cup semi-final losers last week and have already surrendered their Champions League title.
As a result, it is already being reported that interim manager Rafael Benitez could be on borrowed time but, according to McDermott, Chelsea remain a team to be feared.
Since the Spaniard took over his players have excelled on the road - they have scored 23 times in two months - and McDermott knows the threat they will pose at the Madejski Stadium.
"If you look at Chelsea's away record under Rafa it is phenomenal," said McDermott, whose side are unbeaten in 2013.
"They have got a top manager who did fantastically well at Liverpool and also in Spain, and is now trying to work with that group of players at Chelsea. They are a fantastic team but they are not my business.
"You can look at their draw with Brentford but that's just what the cup is all about. Look what else happened at the weekend. Oldham beat Liverpool, (Aston) Villa went out and QPR were beaten at home.
"Chelsea are still in the cup and that's what matters."