Lakers' Robert Sacre -- BURRITO SCANDAL ... I Never Finished 5lb Monster Burrito

Lakers' backup center Robert Sacre has a shocking confession to make ... the 5-pound burrito he reportedly ate a couple weeks ago was stuffed with pork, rice, beans, avocado, and LIES ... 'cause he never actually finished the whole thing.

Sacre -- who had a career game against the Trail Blazers this weekend -- was waiting for his son to land at LAX yesterday ... so we took the opportunity to ask him about the eating contest he entered at El Tepeyac in East LA.

OC Weekly reported that Sacre won the famous burrito challenge by downing all 5 pounds of Mexican goodness ... but the 7-footer admitted to TMZ Sports, he only finished about 3/4 of the behemoth.

To be fair, that's still 3.75 pounds of food ... but at long last, the record is set straight.

Check out the video ... the full story is hilarious.