Ouch.

The two Las Vegas-based love birds, parents and retired tennis pros were participating in an Oprah related reality show and charity event called "The Big Give" when Agassi gave his wife something she did not expect - a smack in the face and the need for three stitches.

They were playing tennis with a couple of kids, trying to give them every chance in the world to win the game.

Agassi was reportedly holding his racket in his left hand - to give the kids an advantage - and holding Steffi's hand with his right. Then whoops ... he took a swing and the racket accidentally smacked her in the lip and cheek.

Fortunately, there was a doctor in the house -- a guy who'd paid a pretty penny ($70,000) to get a chance to play tennis with the two court stars. The Associated Press reported that he stitched Steffi up.

Andre in not in the dog house -- although this has been sited as one of the most embarrassing sports moments of the month. Accidents do happen! Hopefully they are back home and Steffi is healing fast!

The couple was married in Las Vegas in a small ceremony, presided over by a district judge and attended only by their mothers, in October 2001.