The wing-back spoke to iFollow Barnsley after our 3-2 defeat to Portsmouth on Tuesday night.
O'Keeffe entered the fray with just over 20 minutes to play, the scores at 3-1 and the Reds starting to apply the pressure.
The 25-year-old felt that the Reds' display following the break was much more akin to what the side are capable of.
"Obviously, a disappointing result but I think we showed in the second half more of us. If we can play like that for 90 minutes then I think we'll be up there with anyone.
"The gaffer said if we get one early then we can really go at these and that's what we've done. That confidence went up and I thought we took them right to the end, they were dying for the final whistle."
Recently coming back from injury, O'Keeffe was pleased with how he felt out there and how he impacted the game from the bench.
"I felt good when I came on. I feel sharp now after my injury and I can't wait now to get back out there and play.
"They (fixtures) come thick and fast. We'll bounce back now and hopefully get the win."