It was a heartbreaking moment on live TV as Muhammad Ali stunned a sellout crowd on baseball's opening day.

At first, the fans at Miami's brand-new Marlins Park chanted for the 70-year-old boxing legend. But as he rode slowly in a golf cart, his hands shaking uncontrollably from the ravages of Parkinson's disease, the cheers turned to a hush.

The Miami stadium announcer actually had to urge the shocked fans to start chanting again.

Many in the stadium stood silently as Ali prepared to throw out the traditional first pitch. Sadly, one of the Marlins players actually had to gently take the ball from his hand.

Ali's appearance led to an explosion on Twitter:

"Watching Ali tonight made my heart ache," said one tweet.

Another tweet read: "I'm sorry, this doesn't feel right seeing Ali like this."

"Hard to watch," read another.

For others, it's heartbreaking to see "The Greatest" as he is today.