Michael Bay & The Old Spice Guy -- Yeah, We Swing Together

"Transformers" director Michael Bay had a power dinner with the Old Spice dude at Boa in Hollywood last night -- where Bay revealed ... the two sorta play on the same team ... if ya catch our drift.

Clearly, we're talking about softball ... 'cause the two have been teammates for a couple of years.

Bay told us ... "[Isaiah Mustafa] plays on our softball team ... then he got the Old Spice commercials and now we give him s**t."