Long was rested for the season finale against Derby at the weekend - bringing to an end a run of 46 straight starts for the Royals - but is fit and ready to face the Bluebirds at the Madejski on Friday night.
He said: "There is a lot of energy around the place, our squad is very fit and we often outrun teams.
"Perhaps we took our foot off the pedal in the last few games but it was a good win against Derby.
"Hopefully now we can continue where we left off and beat Cardiff over the two legs."
Source: PA
Source: PA