An apparatus having a control circuit including a computer processor and a computer memory configured with computer software. The control circuit causes a first test assembly to conduct an initial test of the air pressure within an inner chamber of a first tennis ball; and if the control circuit determines that the air pressure is below a threshold, a pressurization process increases the air pressure inside the inner chamber of the first tennis ball by piercing the outer skin of the first tennis ball with a needle, until a tip of the needle is in the inner chamber, and a first opening, plugged by the needle, is formed in the outer skin of the first tennis ball. The needle tip is thereafter withdrawn from the inner chamber of the first tennis ball, leaving the first opening unplugged and sealant is applied to the first opening to close the first opening.