The newly-promoted Royals are still without a win since their return to the top flight, and left McDermott disappointed following their 3-1 loss at home to Spurs on Sunday.
But the Reading boss has refused to make excuses for the loss, and has called for an improved performance next time out.
"The last thing we want is to have regrets about a performance, that is the key for me. Since I have had the job we don't go into blame mode or excuse but we would have had regrets after that," he told The Daily Express.
"There was real disappointment in the dressing room after the Spurs game, we all would have had regrets about that game and that performance.
"After the game and when we are sat in the dressing room at West Brom, as long as each and every one of us knows we have done the best we can we will have no regrets about that, and fundamentally when we are at the top of our game we get results."
Reading had not played in the league for 25 days before the game against Tottenham, suffering from a postponement against Sunderland, and the international fixtures that followed.
And McDermott believes that whilst the break was an inconvinience, it shouldn't be used to explain his side's run of form.
He added: "It has been a bit difficult, obviously in the Stoke game we got a point, we went to Chelsea and should have got something and then played Spurs and got what we deserved, we know that.
"We never make excuses but we are glad we have had that game, three-and-a-half weeks is a long time without a game, we were hurting after the game against Spurs because we didn't do ourselves justice."
Reading have picked up just one point so far this season, and the 51-year-old has acknowledged the gulf between England's top two leagues.
"One thing we are is a difficult side to play against and I don't think we would have been seen as a difficult side to play against with Spurs, I think they had a fairly easy afternoon - which hurts us more than anything really," McDermott continued.
"Having said that, we are playing against teams with budgets of millions and millions of pounds - you saw the two finishes from [Jermain] Defoe the other day and that is the difference.
"You have players in this division, world-class players, that make the difference - you have seen that in the Champions League games in the last few days."