Sources: Aaron Judge among six New York Yankees to test positive for COVID-19

All-Star outfielder Aaron Judge was among six New York Yankees players who tested positive for COVID-19 on Thursday, forcing the postponement of their home game against the Boston Red Sox that was supposed to open Major League Baseball's second half and leaving other players on the American League All-Star team undergoing testing to ensure they didn't contract the virus, sources told ESPN.

In addition to Judge, third baseman Gio Urshela and catcher Kyle Higashioka were in the league's COVID-19 protocols after testing positive on rapid tests and awaiting confirmation from a test with greater accuracy, sources told ESPN's Buster Olney. Relievers Jonathan Loaisiga, Nestor Cortes Jr. and Wandy Peralta had confirmed positives and were placed on the COVID-19 injured list, Yankees general manager Brian Cashman said.

"It's a fluid situation that could spread," Cashman said. "It has spread to some degree."

While the rash of positives threw into flux the immediate future of a Yankees team still trying to determine how it will approach the July 30 trade deadline, Judge's inclusion rippled across the league, with players who participated in Tuesday's All-Star Game flying across the country to play a full slate of games Friday. Red Sox third baseman Rafael Devers told ESPN's Marly Rivera that the team's five All-Stars would undergo further testing on Thursday. Unvaccinated All-Stars were tested for COVID-19 while in Denver for the game, and all of the tests came back negative, sources said.

The Yankees, who are in fourth place in the American League East at 46-43, were hoping to put a dent in Boston's eight-game advantage. The Red Sox swept both three-game series against New York in the season's first half, and the teams were scheduled to play eight games over the next week and a half as the trade deadline approaches and the Yankees figure out whether to contend for a playoff spot, punt on the season or hold as is.

This is the second outbreak on the Yankees this year despite the team exceeding the 85% vaccination threshold that allows teams to enjoy relaxed protocols. In May, more than a half-dozen Yankees coaches, including pitching coach Matt Blake, third-base coach Phil Nevin and first-base coach Reggie Willits, tested positive. Nevin spent three weeks in the hospital but credited being vaccinated with saving him from a worse outcome.

"I guess the last year, year and a half, has in some ways kind of prepared you for this kind of stuff," manager Aaron Boone said. "Certainly disappointing and frustrating, and don't want to be sitting here talking about this, and desperately want us to go back to as normal as possible. But that's out of our control, too. And we just got to do the best with the circumstances and with the hand that we're dealt and try to make sure we're taking care of one eat one another as best we can, taking care of our players and staff as best we can. And hopefully get through this."

Among the six Yankees players currently with positive tests, the majority had received a COVID-19 vaccine and were asymptomatic, according to Cashman. Loaisiga went on the COVID-19 injured list Saturday, when the Yankees were in Houston, and did not travel home with the team Sunday.

"We're thankful that we're vaccinated in most cases, not all cases, but in most cases, so we're ultimately protected," Cashman said.

The status of the New York-Boston game Friday at Yankee Stadium remains in flux, and as MLB conducts testing on close contacts and the Yankees scramble to mobilize players to fill out a roster that could be missing nearly a quarter of its regulars, MLB can choose to postpone that game as well.

"You don't want to take any chances," Red Sox manager Alex Cora said. "I think, from my end, playing [two games on Friday] doesn't make sense. Hopefully, we can play one. But the league will decide that."

This was the eighth COVID-19-related postponement this season but the first in nearly three months. Also delayed were a three-game series between the New York Mets and Washington Nationals on April 1-4 and Atlanta's game at the Nationals on April 5, two Minnesota Twins-Los Angeles Angels games on April 17-18 and a Twins-Oakland Athletics game on April 19.

There were 45 regular-season games postponed for virus-related reasons last year with two not made up.

New York was among the first major league teams to reach the 85% vaccination threshold to lessen coronavirus protocols such as dropping mask use in dugouts and bullpens.

MLB said in its last announcement on June 25 that 23 of its 30 teams had reached an 85% vaccination rate among Tier 1 individuals, such as players and on-field staff. The Red Sox were not among them.

New York players were taking early batting practice about 3½ hours before the scheduled start Thursday when the Yankees asked media to leave the field while the team conducted COVID-19 testing. Boston, whose 55-36 record matched Houston for best in the AL, came onto the field to take batting practice as the postponement was announced.

The Associated Press contributed to this report.