UCLA basketball star Shareef O'Neal -- Shaq's son -- says he'll be forced to sit out next season due to a heart issue that will require major surgery ... but vows to return ASAP.
TMZ Sports spoke with the 18-year-old superstar who said he was having a routine checkup recently when the docs "found a medical issue dealing with my heart."
Shareef didn't specify the exact problem -- but said the issue is severe enough that he'll be having heart surgery in the near future.
"Thank God the UCLA medical staff caught it early," O'Neal tells us.