PHILADELPHIA -- The Phillies believed they implemented and executed “airtight” procedures to prevent the spread of COVID-19 at their Clearwater, Fla., facilities, where a handful of players trained since March, when Major League Baseball cancelled Spring Training because of the pandemic.

Still, six players and several staff members there recently tested positive for the virus. A seventh player outside of Clearwater also tested positive.

It illustrates the challenges the Phillies and 29 other teams face as they begin summer camp on Friday and look ahead to playing a 60-game season, beginning July 23 or 24. Phillies general manager Matt Klentak discussed those challenges and concerns during a video conference call Monday afternoon.

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“We’ve been fairly fortunate that none of the cases, players or staff, have been especially serious,” Klentak said. “Some of our people have had flu-like symptoms and fevers that have lasted anywhere between a few hours and 24 hours. But nobody has been hospitalized. There haven’t been any grave concerns for anybody, which is good obviously. I think what is eye opening to a lot of us is how quickly it spread, even in an environment where we were on the extreme end of caution. The facility in Clearwater was pretty airtight in terms of staggering the times that players were reporting and working out and cleaning the facilities in between.

“Truthfully, in some ways it was frustrating to some of the players how strict it was and yet this type of outbreak still happened. So it’s concerning, but at the same time I’m hopeful that not only our team but teams throughout the league can learn from what happened on the eve of Spring Training and hopefully work to prevent more outbreaks like this moving forward.”

Some players across baseball -- mostly notably Ryan Zimmerman, Mike Leake and Joe Ross -- have decided not to play this season due to coronavirus concerns.

Klentak said he doesn’t expect any Phillies to choose not to play, although everything is subject to change. The Phillies announced 53 players on their 60-man player pool Sunday. Klentak said Monday that right-hander Anthony Swarzak will be added to the list, bringing the number to 54.

There will be more.

“That's a product of just wanting to make sure we preserve enough flexibility,” he said. “There's enough uncertainty with COVID, with the rules that are constantly being adjusted, with players traveling in -- we wanted to make sure we preserve the ability to adjust. Once a player is on, it's very hard to get them off the 60-man roster without releasing them or doing something relatively permanent. We thought it was best to leave some room. We can always add. But it's much harder to subtract.”

Players have started to arrive in Philadelphia. They will train at Citizens Bank Park as well as across the street at the MLB Urban Youth Academy fields at FDR Park. Once the season starts, players not on the active roster will work out at Coca-Cola Park in Allentown, Pa., the home of the Phillies’ Triple-A affiliate.

What players see and experience at the ballpark could come as a shock, such as staggered workouts throughout the day.

“We’re working on the clubhouse to make sure guys can separate -- in the weight rooms and the training rooms, as well,” Klentak said. “We’re looking to use all parts of the ballpark so it’s an all hands on deck process coordinating with our ballpark ops folks and our facility folks. It’s not going to be surprising to see guys doing weight room routines on the concourse. That’s something we’re contemplating just to give guys a little more room to maneuver.

“We are asking all of our players and staff to be flexible to recognize that things are not going to look and feel the same way that they have in their careers, particularly the players that have been in our uniform and in our clubhouse before. Some things will be different. And we’re asking everybody to be flexible. Everybody, no matter what your role is in this industry, has an incentive to make these games go. That’s what we want.”

But Klentak acknowledged that what happens away from the ballpark is not under the team’s control.

“It’s going to be a challenge,” he said. “It’s going to take a lot of discipline from a lot of people. It’s going to put a lot of strain on the testing process. The importance of testing every couple of days is going to be critical to the operation as is the discipline of the people to stay safe, not only when they are at the field but when they are not at the field. Everybody wants the same thing. We want baseball to come back, we’re thrilled that we’re coming back, but just because we announced we’re coming back doesn’t mean we can take our foot off the gas. We need to make sure that we double down on our efforts to make sure that when we are back, we stay back.”