Formula Shell Zoom Masters / Shell Velocity Castillo was drafted 2nd overall by the
San Miguel Beermen in
1998 but was traded on draft day to the
Formula Shell Zoom Masters for 1st overall pick
Danny Ildefonso. As the rookie starting
point guard, he, alongside two-time MVP
Benjie Paras,
Gerry Esplana,
Vic Pablo, and
Chris Jackson, led the franchise to back-to-back titles in the
1998 Governors’ Cup and
1999 All-Filipino Cup in the start of his sophomore season.
Purefoods Before the start of the
2000 PBA Season, Castillo was acquired by
Purefoods TJ Hotdogs, who traded a 2002 first-round draft pick for his services. Shell traded him to make room for the salaries of Paras and Esplana, and so that he could go to a team where he could have more minutes. In the
Governors' Cup, he helped the team make the semifinals. Castillo led the team in scoring in
2001, taking the team to a semifinals appearance in the
2001 Commissioner's Cup. He made the All-Star team that year, competed in the Two-Ball Competition, was awarded as the
Most Improved Player and became a member of the
Mythical Second Team. During that season, he played through a toe injury, one he wouldn't get surgery on until after the season. Castillo won his first title with Purefoods during the
2002 Governor's Cup. He also spent most of the
2002 season on loan to the
Philippine national team alongside teammates
Andy Seigle and
Boyet Fernandez. They made their return to the team during the
All-Filipino Cup. In 2006, Purefoods, now known as the
Purefoods Chunkee Giants, made the
2005–06 Fiesta Conference finals against
Red Bull Barako, losing in six games. During the
Philippine Cup, Castillo strained a calf muscle, causing him to miss several games. He returned in time during the semifinals to become a key weapon in their title run. During the
finals, in a rematch against Red Bull, he missed all six of his three-pointers in Game 3. Despite this, he was able to make contributions throughout the finals, especially in Game 6, as Purefoods was able to win this time over Red Bull in seven games. He was also named as an All-Star during the same season. During the
2007–08 season, he played in the
2007–08 PBA Philippine Cup finals against the
Sta. Lucia Realtors. Sta. Lucia went on to win the finals in seven games. Because of recurring injuries, he retired from basketball in 2008. ==National team career==