NEW YORK -- Spring training could be delayed for Double-A and Class A players if major leaguers are not vaccinated for the coronavirus by the time big league practice is scheduled to start in mid-February.

Major League Baseball, which has taken over operation of the minors, gave notice to minor league teams and big league clubs on Monday.

"We are still evaluating many issues that affect both the major league and minor league schedules, including, most importantly, when it is likely that players and staff will be vaccinated," Peter Woodfork, MLB's senior vice president of minor league operations and development, wrote in a letter to big league clubs that was obtained by The Associated Press.

The letter was first reported by Baseball America.

"Assuming that a vaccine is not available to players and staff at the beginning of major league spring training, there is a strong possibility that minor league spring training will be delayed for players who otherwise would be assigned to Double-A, High-A, and Low-A because clubs have informed us that there is not sufficient space at spring training facilities for all of the players in an environment requiring strict physical distancing," Woodwork wrote.

He said under that scenario, those minor leaguers would report to spring training after big leaguers and Triple-A players leave for opening day "unless it is necessary to utilize the alternate site arrangement at the beginning of the season" as MLB did for health reasons last year.

Woodfork wrote that MLB "will let minor league clubs know as soon as possible of any modifications to their facilities that are required in 2021 in the event we need to play prior to the vaccination of players. They in turn will let us know whether they desire to operate in the event that government restrictions prevent them from having fans, or significantly restrict the number of fans allowed in their ballparks."

Woodfork said MLB will attempt to schedule as many minor league games as possible subject to health conditions.

"We do believe that by the second half of the 2021 season, the operation of the minor leagues should be much closer to normal than in the early part of the season," he wrote. "While the current uncertainty about the vaccination timeline for our players and staff, and the state of COVID-19 in our country in the spring and early summer, makes it difficult to create a schedule at this time, we intend to begin the process and make adjustments as things become clearer."

Schedules and league alignments are subject to COVID-19 conditions and clubs signing MLB's license agreements for the minors.

Big league spring training remains on track to start on time in mid-February and opening day is set for April 1, but a final decision for an on-time start has not yet been made. As of now, no timetable has been set to vaccinate big leaguers.

Many players who start the season in Triple-A report for the start of big league spring training and then are optioned to the minors. Players in the lower levels of the minors usually report later in spring training.

Spring training was interrupted by the pandemic in mid-March last year, and the big league regular season was delayed until late July and shortened to 60 games. All 2020 minor league seasons were canceled.