EXCLUSIVE

Al Michaels -- perhaps the most well-known sportscaster in the world -- was arrested Friday night for suspicion of DUI ... TMZ has learned.

Law enforcement sources tell TMZ ... Michaels went through a DUI checkpoint in Santa Monica at approximately 10:00 PM on Friday and when he spoke to officers, they detected an odor of alcohol.

We're told he was pulled over and given a field sobriety and after performing poorly, he was placed under arrest. Michaels was released from jail at 4:15 AM on Saturday on his own recognizance.

According to our sources, Michaels blood alcohol level was right at the legal limit -- he blew a .08 and a .09 in two breathalyzer tests.

Our sources say Michaels could not have been nicer throughout the ordeal.