COVID-19 Update: Changing Plans, Inconclusive Tests

To the surprise of no one, COVID-19 continues to affect the baseball season. Plans have changed and re-changed as two teams have seen clusters of positive tests. While this news is, as always, subject to change, here’s our most recent update.

The Marlins In Purgatory

As of now, the Marlins are scheduled for a Tuesday game in Baltimore. There is, as yet, no information on which players will be available, but the Marlins are behaving as if they’ll need some new blood: they’ve acquired Justin Shafer, Josh Smith, Mike Morin, and Richard Bleier in the last week, and signed Logan Forsythe. Given that the league’s testing protocol requires two negative tests more than 24 hours apart before a player can return to the field, they may need even more reinforcements on the hitting side as well.

The Marlins players who tested positive for COVID-19 took the bus back to Miami. That group comprises 18 players, which left 12 of the initial 30-man roster in Philadelphia awaiting their next move — minus Isan Díaz, who opted out of the season over the weekend. Those 11, plus the four new pitchers, will join players from the 60-man player pool to form what passes for a major league roster and play against the Orioles.

The long-term effects of the last week’s postponements will be harder to plan. The Marlins have played only three games this year, which leaves them with a lot of ground to make up. They were originally scheduled to play Philadelphia in Miami this week before the Orioles and Yankees played an impromptu series to minimize cancelations. At some point, the team will be more or less back to its initial form, and they’ll have a lot of games to play.

Phillies Resume Play

The Phillies played no games last week after their potential exposure to Marlins players during their weekend series. Three employees tested positive for COVID in the team-wide testing done after the Marlins series: a coach, a home clubhouse staffer, and a visiting clubhouse staffer. The coach and home staffer’s tests were both, per the league, false positives, which means no players or home staffers tested positive for the coronavirus after the Marlins game.

Even so, the team has played only three games this year. They’ll resume play today in New York against the Yankees, with just as many games to make up as the Marlins, though with a far more complete roster. The normal weather-related complications of playing baseball in August will figure in as well — the Phillies faces an uphill road to the playoffs despite not having any positive tests among their players. That is unquestionably good (and far more important) news than the vagaries of their remaining schedule, but serves to underscore the difficulty of staging a season amidst a pandemic, even with everyone healthy.

Cardinals Await Clarity

After two Cardinals tested positive for COVID-19 before their series opener against the Brewers on Friday, the game was postponed. As more tests came in over the weekend, the entire series was canceled, as was the series against the Tigers. The general trajectory does not look good.

There are more tests still coming in, which has added to the confusion. Four further tests over the weekend — belonging to three staff members and one player — were inconclusive. Additionally, another player, who the team expected to test positive based on contact tracing of the two initial positive tests, also tested positive.

The team announced that it expects new testing results today, which could shed light on its next steps. While player names haven’t been released, the team has isolated those with confirmed positive tests — two have already returned to St. Louis — with the goal of continuing their season more quickly than the Marlins did.

Update: Per Mark Saxon, more positive tests have come in. The team announced that a total of 13 members of the organization have tested positive, including seven players. This means that five additional players have tested positive. The series in Detroit has been canceled, with potentially more to follow. We’ll update the story with more results as they become known, but for now, it looks like the Cardinals failed to contain the spread of COVID.

Brewers Back on Track

While the Brewers missed a three-game series with the Cardinals, they never had any exposure, potential or otherwise, to the team. The Cardinals never even saw Miller Park, as they arrived in Milwaukee on an off day and were in lockdown at their hotel by 6 AM the next morning. The Brewers home opener, originally slated against the Cardinals on Friday, will instead be against the White Sox today.

The team didn’t escape the weekend without bad news, however. Bench coach Pat Murphy suffered a heart attack during a team activity on Saturday. Thankfully, he’s recovering well, and could leave the hospital as early as this week. Milwaukee will also be without two lineup stalwarts: Lorenzo Cain opted out of the season on Saturday and Ryan Braun hit the Injured List with an infected index finger.

At this point, it’s clear that a season free of COVID-19 interruptions is out of the question. Hopefully, there are no further outbreaks. If there are, however, the course of the Cardinals situation will be instructive for the league. The Marlins’ 20-person outbreak, if repeated elsewhere, would surely force an end to the season. St. Louis’ relative inability to contain positive tests is a dire sign. Better control might allow the season to continue with fewer delayed games and wholesale changes to the schedule — assuming, of course, that MLB’s revised health and safety protocols prove to be effective. We have to hope they will be. Much more than baseball is on the line. At the moment, however, things look grim.

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Ben is a contributor to FanGraphs. A lifelong Cardinals fan, he got his start writing for Viva El Birdos. He can be found on Twitter @_Ben_Clemens.

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So, what’s with all the inconclusive tests/false positives? I haven’t been obsessing over the news during this time (I value my sanity), but I don’t recall hearing about such a high false positive rate. It sounds like it’s a big contributor here. Are they they using a bad test or this to be expected?


Basically every biological test has a chance to produce a false negative or false positive. I’m not an expert (my limited experience in this basically comes from a few statistics classes) but it’s my understanding that generally they are tuned to have as small a false negative rate as possible, sometimes at the expense of having a higher false positive rate – the thought being you’d rather people be cautious and isolate, etc. rather then give a false sense of security and have them go out and unwittingly spread the disease to others. With covid 19 being so new many of these tests are still not all that accurate or precise, relatively speaking. So yes, this is to be expected, and is really not out of the ordinary. Unfortunately this all moot now as it seems many positive cases in the Cardinals organization have been confirmed today anyway.


The COVID-19 nasal swab PCR test has a very low false-positive rate, usually due to technical errors and reagent contamination. Positive results from those tests are pretty reliable.

The inconclusive tests/false positives are probably because MLB is using saliva tests rather than the more accurate nasopharyngeal swab test. Since most of the tests are being analyzed in MLB’s contracted PED lab in Utah, the testing issues could be due to operator error (because this is the first time the lab is doing PCR tests ), problems with the sensitivity of testing saliva, or some other reason.