Avoid recording calls on the same day - the call center agent may be just not feeling well, or in a bad mood and all recorded calls may reflect this kind of negativity which may not really be the call center agent's usual work performance.
Listen to the calls and take note of the call's opportunities and strengths. Note what the call center agent did during the call to make the call great and determine several opportunities for performance improvement before meeting with your employee.
Play the recordings and together with the call center agent, listen to the recordings. After listening to a call, ask the call center agent to evaluate the quality of the call. The call center agent will point out several opportunities for improvement.
When you start coaching, remember to use the "sandwich" technique -- good/bad/good. Tell the call center agent the positive things that transpired during the call, followed by a constructive feedback, and end with another optimistic feedback. Share only one opportunity for improvement during the constructive feedback. The call center agent has likely provided a number of opportunities for improvement during the call so stating them again would be unnecessary. You can try to mention one opportunity that the call center agent failed to identify and use this for your constructive feedback.
You need to have the agent commit himself for performance improvement. You can do this by asking the call center agent what he plans to do over the next five days in order to improve his work performance. Jot down that the call center agent said and read it again to the call center agent. Close the session by reiterating the positive aspects of the call and provide a vote of confidence that the call center agent can improve his work performance.
With the remaining one or two recordings, repeat the whole process. Reviewing two or three recorded calls is important especially when the call center agent defensively reasons that the first call was just a "bad call". if the agent insists that it was just you caught him on a bad day, then you can just review the remaining recorded calls.