Harris' agent Jack Bechta said the 33-year-old veteran had some internal bleeding and the initial diagnosis is that he ruptured his spleen, according to the Milwaukee Journal Sentinel.
"He would most likely miss the season, it would just depend on the severity," Bechta told the newspaper. "But we don't have any definitive information except there was a rupture. Now we have to get him to a specialist as soon as possible."
And while nothing is definitive, Bechta said the odds of Harris returning this year aren't good.