We got the "Beverly Hills, 90210" alum at Bristol Farms in Woodland Hills, and the 50-year-old actor told TMZ it wasn't wise of Chelsea to compare herself to his ex-wife. He candidly shared, "It seems like you're opening yourself up to criticism."

ICYMI ... when discussing their physical appearance while on the sight-unseen dating show -- Chelsea informed her future fiancé, Jimmy Presnell, she had previously been compared to the "Jennifer's Body" star.

Infamously, Jimmy did not agree with the comparison upon their first meeting out of the pods.

On whether he feels the comparison has any merit ... Brian told us it was tough to say -- since Megan is a "one-of-a-kind beauty," and "possibly the most beautiful woman in the world."

Brian and Megan were married for 11 years between 2010 and 2021, welcoming 3 children together. He is now engaged to "Dancing With the Stars" alum Sharna Burgess, with whom he shares a son, Zane Walker.

Still, Brian thinks critics should give Chelsea a break, especially since MF won't care one iota about the remark. In fact, the "Anger Management" star told us, "I think Megan would be flattered."

Brian, who just launched a free social media app on the Apple Store called Moviac, encouraged Chelsea not to listen to the haters, which is certainly easier said than done.