UP Fighting Maroons Gregorio was hired as the head coach of the
UP Fighting Maroons of the
UAAP in 2000. and he was replaced by his brother Allan in 2002.
Purefoods In 2002, Altamirano was selected to be as an assistant coach for the
Philippine National Basketball Team, and Gregorio was named as the interim coach of the TJ Hotdogs. Under Gregorio's hands, Purefoods won the 2002 Governor's Cup with a 4–3 series victory over the
Alaska Aces. The team was led by imports Derrick Brown, Kelvin Price and Best Player of the Conference winner
Rey Evangelista. Gregorio coached the team to a dismal performance in the Commissioner's Cup before Altamirano regained coaching duties in the All-Filipino Cup. Despite this, Gregorio was rewarded, along with then-
Coca-Cola Tigers mentor
Chot Reyes as co-winner of the PBA Press Corps Coach of the Year Award. In
2003, Gregorio became the full-time head coach of Purefoods, after Altamirano was tasked to head the San Miguel All-Stars team. In the
2004–05 season, Gregorio coached the Purefoods team, retooled with amateur stars
James Yap,
Paul Artadi,
Peter June Simon and the vastly improved
Kerby Raymundo. Purefoods would have losing records in the 2004 Fiesta Conference. The team marginally improved to finish two quarterfinals' stints in the Philippine Cup and the 2005 Fiesta Conference. The
2005–06 PBA season would be Gregorio's finest season yet, he would lead the Purefoods Chunkee Giants to two finals appearances, a runner-up finish in the
2005–06 Fiesta Conference, and a championship against
Red Bull in the
Philippine Cup Finals, winning in 6 games, 4–2. Prior to the finals meeting with Red Bull, he would bring his team back to life after being down 1–3 in the semifinals against Alaska. The series victory against Alaska would be remembered as one of the best comebacks in the PBA history. He once again coached his team to its second championship in the last four years. The 2006 success earned him his second Coach of the Year Award. Gregorio started the 2007–2008 season with a bang. He led his team to a 5-game sweep of the pre-tournament games and would eventually bag the Pre-Tournament Championship. He would continue his mastery of the All-Filipino Conference as he led his team to a 7–0 start and finished with 12 wins and 6 losses, enough to push the team to the semifinals. He would lead his team to another trip to the Finals, his third. However, his team would eventually lose to
Sta. Lucia in 7 games via a controversial series. The
2008–09 PBA season became one of Gregorio's worst seasons. Starting center
Rommel Adducul was diagnosed with throat cancer and forced
Purefoods TJ Giants to trade key player
Marc Pingris to
San Miguel Beermen for big man
Enrico Villanueva. This signaled a major revamp with Gregorio's team lineup and a losing season finishing with only 15 in 32 elimination round games. He only managed to stir his team through the wildcard in both conferences. His team would end both tournaments in controversies, a bottle-throwing incident between his player
James Yap against assistant coach Koy Banal and the benching of reinforcement
Marquin Chandler on separate do-or-die games the TJ Giants consequently lost. Gregorio guided his team in the
2009–10 PBA season to a record 41 wins. James Yap would earn his 2nd season MVP award. With the return of old reliables
Marc Pingris,
Paul Artadi together with veteran center
Rafi Reavis, and rookie standout
Rico Maierhofer, his team would finish as champions in the
2009–10 PBA Philippine Cup Finals defeating the
Alaska Aces, 4–0. The sweep is the first time in the history of the All-Filipino Conference. He is also concurrently part of
Meralco's corporate staff as Assistant Vice President and Head of Meralco Sports and Youth Advocacy. His five years coaching stint with the Bolts would prove to be dismal as he was unsuccessful to lead Meralco beyond the quarterfinals. Assortment of injuries to key players, and trades that hurt the team's chemistry contributed to the Bolts downfall. In July 2014, Gregorio declined the offer to return as head coach. Instead, he opted to concentrate on his corporate affairs role with Meralco. ==Coaching record==