Magsanoc played collegiate ball with Benjie Paras, Eric Altamirano, future UP head coach Goldwin Monteverde and Joey Guanio for the University of the Philippines basketball squad, then coached by Joe Lipa, where he helped the Fighting Maroons win the UAAP championship in 1986, their first basketball championship in 48 years.

[3] Magsanoc joined the Philippine Basketball Association in 1988 and was picked by Shell while his former national teammates Jojo Lastimosa, Glenn Capacio, Jerry Codiñera and Alvin Patrimonio were absorbed by newcomer Purefoods Hotdogs in one of the best entries of freshman cagers to the pro ranks.

The triumvirate of Magsanoc, Paras and seven-time best import Bobby Parks led Shell to the finals in the first conference each year from 1989 to 1992, winning two championships and placing runner-up twice.

From 1993 to 1995, he remains one of the top point guards despite Shell missing the finals trip for three seasons and with the emergence of Alaska's Johnny Abarrientos.

[7] In 2013, he was enshrined into the PBA Hall of Fame, along with Paras, Lim Eng Beng, and the late Ed Ocampo.

[12][13] He also served as an assistant coach for the Ateneo Blue Eagles, a collegiate varsity team in the Philippines.