Cain, a married father of three young sons, said he made the decision "after careful consideration and discussion with my family."
"With all of the uncertainty and unknowns surrounding our game at this time, I feel that this is the best decision for me, my wife, and our three kids," Cain said Saturday in a statement released by the Brewers. "The Brewers organization was very understanding and supportive of my decision, and I thank them for that. I wish all of my great teammates the best of luck this season and look forward to getting back on the field in 2021. Please stay safe."
The two-time All-Star's decision was announced as the Brewers' scheduled home-opening series against St. Louis was postponed because multiple members of the Cardinals tested positive for the novel coronavirus.
"He felt this was something that he needed to do," Brewers general manager David Stearns said. "We completely respect the decision and support the decision. This is something that Lorenzo had been thinking about and discussing with his family for some time. This is the first he had brought it to our attention, but as we understood the decision and understood the decision-making process, it's something that's been on his mind and ultimately he believes this is the right thing for him to do and we understand that."
Cain was 6 for 18 with two RBIs in his first five games this season after batting .260 with 11 homers, 48 RBIs and 18 steals last year, when he earned his first Gold Glove. He has a $5,925,926 prorated salary this season as a part of an $80 million, five-year contract through 2022.
"I think it's fair that the events of the past week I'm sure played a part [in Cain's decision]," Stearns said. "He did not specifically mention the Cardinals or the Marlins, for that matter. I think this was just something that he had been considering, thinking about, discussing with his family and ultimately it just got to the point yesterday where he was ready to make his decision."
The exit of the 34-year-old Cain leaves the Brewers without one of their biggest leaders as they attempt to make a third straight playoff appearance, something they've never accomplished in franchise history.
Cain finished seventh in the NL MVP balloting in 2018 when teammate Christian Yelich won the award and the Brewers ended up one win away from the World Series, losing to the Los Angeles Dodgers in a seven-game NL Championship Series. Cain ranked fourth in the NL in on-base percentage (.395) and steals (30) and fifth in batting average (.308) that season.
He wasn't fully healthy last year but still helped the Brewers earn a wild-card playoff berth.
"It's going to hurt," Stearns said. "Lo is a big part of this team. He, from a physical standpoint, was in a great spot this year. His body felt really good. I think we saw that through summer camp and the first week of the season. He's in great shape and playing at a really high level right now, and we were going to get a really good season out of him, and so we will miss that and the energy he provides."
Cain's absence may result in more opportunities for Ben Gamel, a versatile outfielder who made 36 starts in left field, 15 in right and 14 in center last season. Gamel was one of Milwaukee's hottest hitters throughout its summer camp and has followed that up by going 3 of 12 with a homer and a triple in four regular-season games.