NEW YORK (Reuters) - Tens of thousands of Major League Baseball (MLB) fans will return to regular-season games across the United States this week for the first time in 18 months, in a radically different landscape amid the COVID-19 crisis that nearly caused last season to be derailed. Eleven ballparks served as mass COVID-19 vaccination sites during the offseason, administering more than 1 million doses, in stadiums where MLB now hopes to welcome back fans - slowly, at first - over a 162-game season, after the entirety of 2020’s regular season was played to empty stands. “Sports operate on the entire idea of getting people addicted to their product,” said Victor Matheson, a professor at College of the Holy Cross and an expert on sports economics. “The question is whether, you know, a year or 18 months or two years has allowed you to kick that addiction, and whether people actually say, ‘Yeah, you know what? I’m not sure I’m ever going back in the same way I did before.’” It is a critical point for MLB, which fared worse than the National Basketball Association, the National Hockey League and the National Football League over the last 12 months, with MLB’s revenue plummeting by more than $6 billion between 2019 and 2020, according to Matheson. The MLB regular season starts on Thursday with all 30 teams scheduled to play. Last year’s delayed start to the season, which was shortened to just a 60-game schedule, and the decision to not allow fans except at the National League Championship Series and World Series, took a chunk out of the league’s bottom line. “They fared terribly last year and that was a combination obviously of no fans as well as only 40% the number of games and, for example, playoff ratings were terrible,” said Matheson, adding that the Los Angeles Dodgers’ successful championship bid was the least-watched World Series ever. As MLB works to bounce back from its annus horribilis, fans can expect new health and safety protocols at ballparks across the country, with all the clubs allowing at least some fans to attend their games including the Texas Rangers, the only team that will start its season with 100% capacity. Basic measures like mask-wearing and social distancing will be part of the protocol at all stadiums, while individual teams will be permitted to enforce their own enhanced measures. While MLB did not mandate a COVID-19 vaccine or test for fans, the New York Yankees and New York Mets, which are each allowing 20% capacity to start the season in accordance with state guidelines, will require attendees to show proof of inoculation or a negative test. The Milwaukee Brewers, which will operate at 25% capacity, last week said they were going entirely cashless inside American Family Field and said they were encouraging fans to opt for mobile concession ordering. “That’s just going to be right now, for the short term, the cost of doing business,” said George Belch, a San Diego State University marketing professor and co-founder of the school’s Sports Management MBA program. “It’s not unlike what they’ve gone through ... with the expensive testing almost every day of the players in football and baseball, basketball.” MLB reported on Friday two new COVID-19 positives among players and two among personnel in its weekly testing results. “They have to be excited and really hoping that they can not only get people in but be able to increase the number throughout the season,” said Belch. “It’s not only for the ballpark, it’s just for the person you know watching on TV.” ESPN Senior Coordinating Producer Phil Orlins told reporters that even on the broadcast there is an “authentic sound” of a crowded ballpark that can’t be replicated. “I just miss the kid or the father catching the home run,” said Orlins. “I miss the fun.”