A teammate of Bucks infielder Kevin Welsh at Rutgers, Reardon played four years of varsity baseball at North Brunswick under former Rutgers third baseman Ryan Lillis. The lefty holds the North Brunswick record for home runs (10) and pitching wins (14) and participated in the 2015 and 2016 NJ State All-Star Games. Reardon was named the 2015 Greater Middlesex County Player of the Year and Home News Tribune Player of the Year and was an all-state selection with a .406 batting average, seven home runs, 26 hits, 25 RBIs, five pitching wins and a 1.63 ERA as a junior. The two-time team captain and all-division selection was also a three-year varsity basketball starter, serving as a team captain as a senior. Reardon joined the Scarlet Knights in 2017 as a true freshman, going 2-1 with a 6.44 ERA in 21 appearances and 1 start. In 2018 the southpaw improved his numbers by posting a 4-2 record with a 5.45 ERA in 16 appearances and 6 starts. The swingman struck out 23 over 33.0 innings with a .242 opponent batting average.