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Dwyane Wade was REALLY close to heading west instead of reuniting with his bestie LeBron James this off-season ... so says ex-NBA star Caron Butler.

TMZ Sports spoke with Tuff Juice about his convo with Wade before he made his decision to join the Cavs ... and he says Wade was seriously considering Miami, OKC and the L.A. Lakers.

Butler breaks it down -- L.A. made sense considering Wade's movie star wife Gabrielle Union, OKC would've been a good basketball move, and Miami's his first NBA home.