"I hope people see what happened to us and use that as a warning if you're not following the protocols 100%," Jeter said. "You can't let your guard down. We're battling something that is invisible.''
The Marlins haven't played since July 26 due to a coronavirus outbreak, which included positive tests for more than half of the team's players and two coaches.
Now, after two consecutive days of no more positive tests, the Marlins are scheduled to return to the field Tuesday for the first game of a four-game series against the Baltimore Orioles in Baltimore.
The healthy members of the Marlins have traveled from Philadelphia to Baltimore to face the Orioles. The 18 players who tested positive returned to Miami by bus last week and will stay quarantined in the Marlins' home city.
Player expected back
Jeter said the conditions of the Marlins players who tested positive range from asymptomatic to "mild" illness. He expects the 18 players to return, but did not give a timetable.
Jeter said Marlins players are upset with reports that they left their hotel and went to bars, which could have made them more likely to contract COVID-19. Jeter denied those reports, but admitted Marlins players were not always wearing masks and were not social distancing properly.
"We have to be better. We have to be perfect," Marlins manager Don Mattingly said. "We know the spotlight is going to be on us with this whole thing."
Jeter said some players left the team's hotel in Atlanta during a preseason series against the Braves to get coffee and clothing. That was just days before the team's season-opening series against the Phillies in Philadelphia.
"There was no hanging out at bars," Jeter said. "No clubs, no running around Atlanta. What it boiled down to was guys were around each other, they got relaxed and they let their guard down. They were getting together in groups. They weren't wearing masks as much as they should have."
Jeter denied reports that Marlins players on their own decided to play the Phillies in Philadelphia in the final game of their series after they learned about Miami's four positive COVID-19 tests.
Jeter said MLB and Phillies and Marlins players and management all were aware of the situation and decided to proceed with the game.
"Our players and coaches went into this [season] knowing their health was on the line," Jeter said. "They have had to endure quite a trying time over the last week-plus. We have seen firsthand just how contagious this virus is.
"After we left spring training and had numerous discussions, some of our traveling party had a false sense of security and comfort in how they handled themselves after we left Miami," he said.
With so many players sidelined, Miami has revamped its roster. Fans will see a collection of younger players and veterans pieced together through promotions, trades and recent signings.
MLB also has increased its safety standards for the coronavirus. A COVID-19 protocol compliance officer now will travel with the Marlins and every other MLB team.
MLB continues to investigate the cause of the Marlins' outbreak, but Orioles manager Brandon Hyde said Saturday that his team is "comfortable" with the Marlins playing in Baltimore.
"We're trusting MLB and I feel really strongly that we've followed the protocols so well here," Hyde said. "I know that MLB is on top of it.
"If they feel like they're comfortable with them playing here, I'm comfortable, as well, just because I know how stringent our protocols are and how they're keeping the players health and safety first for everybody."
The Marlins are scheduled to be on the road for 24 consecutive days as part of their altered schedule. They are to return to Miami on Aug. 14.
The Marlins and Orioles will play beginning at 7:35 p.m. EDT Tuesday at Oriole Park in Camden Yards. The Marlins originally were scheduled to host the Orioles July 27 and 28 before they were to play in Baltimore on Wednesday and Thursday.
Dates for the Marlins' suspended series against the Washington Nationals and the Phillies are to be announced later.
Nine MLB teams have had their schedules impacted since the season started as a result of positive COVID-19 tests.
Cardinals have second outbreak
The Phillies also haven't played since July 26, but they were scheduled to resume their season against the New York Yankees on Monday in New York City. They will skip Tuesday because of anticipate heavy rain from Tropical Storm Isaias and play a doubleheader in Philadelphia on Wednesday.
Philadelphia announced Monday that it didn't have any positive tests Sunday. On Thursday, two staff members tested positive for the coronavirus, but no further issues have been reported for four consecutive days.
All of MLB's initial game postponements were tied to the Marlins outbreak before the announcement Friday that two members of the St. Louis Cardinals had tested positive.
The Cardinals' outbreak has since grown to 13 positive tests and includes seven players and six staff members. MLB on Monday also postponed the Detroit Tigers and Cardinals series, planned for Tuesday through Thursday. The Cardinals had a series against the Milwaukee Brewers this past weekend postponed.
Cardinals players have been in quarantine since Thursday in Milwaukee and will continue to be tested daily, league officials said.
"The tentative plan is for the team to resume its regular schedule on Friday against the Chicago Cubs in St. Louis," MLB said.
The Marlins, Phillies, Orioles, Cardinals, Brewers, Tigers, Toronto Blue Jays, New York Yankees and Washington Nationals are the teams whose schedules have been changed due to positive test results.