The 2020 Major League Baseball season, upended by the COVID-19 pandemic, was delayed by nearly four months. The typical 162-game scheduled ultimately was shortened to 60 games, and teams played in empty ballparks due to health and safety protocols.

So as Opening Day 2021 approached, fans had many questions, such as, “Is baseball coming back in 2021?” and "Will MLB allow fans in stadiums?" among other things. To help with that, here is a complete guide to everything you need to know about the 2021 MLB season.

MLB Rule Changes 2021
The expanded postseason we saw in 2020 is not returning in 2021, with the field decreasing from 16 teams back to 10. But what about other rules changes?

• The universal DH also is out for 2021 after debuting last year. That means the DH is only being used in AL ballparks, while pitchers are back to hitting in NL ballparks. On Opening Day, Arizona's Madison Bumgarner -- perhaps the most accomplished hitting pitcher of his generation -- celebrated with a long double. Adrian Houser of the Brewers hit the first pitcher home run of 2021 on April 27, and the Braves' Huascar Ynoa followed a day later, then launched a grand slam on May 4.

• Two other rules that were implemented in 2020 in an effort to minimize the time spent at the ballpark have returned in 2021. First, doubleheaders are once again featuring two seven-inning games. Also, MLB's extra-innings rule is back, meaning that beginning in the 10th, a runner is being placed on second base to begin each half-inning.

• Rosters once again feature 26 players, after expanding in 2020. Roster size will increase to 28 players in September. There will not be a limit to how many pitchers can be on a team's roster.

• Clubs may bring a "Taxi Squad" of up to five players on all road trips, in order to have reinforcements available in the event of injuries or COVID-related issues.

MLB and COVID-19
Last year, the arrival of the coronavirus pandemic shut down Spring Training in mid-March and delayed Opening Day. The 2020 season did not begin until late July, and teams played a 60-game schedule, adhering to MLB's strict COVID rules. They then embarked upon an expanded postseason.

Nearly a year later, the pandemic persists, although ongoing vaccinations -- including many at Major League ballparks -- are providing hope. However, COVID-19 is continuing to affect MLB in 2021. That extends to both fans (in terms of how many are allowed to attend games) and players (who once again have to abide by health and safety protocols). As vaccinations continue, though, restrictions are loosening. When a team gets 85% of its Tier 1 Individuals (including players, coaches, trainers and some front-office members) fully vaccinated, MLB and the MLB Players Association have agreed to relax some of the health and safety protocols.

The regular season, All-Star Game and postseason
Until last year, there were 162 games in an MLB season. That will be true once again in 2021, with the league sticking to its previously released schedule, which runs from April 1 through October 3. Unlike during the abbreviated 2020 campaign, clubs are not limited to playing opponents from the same region (West, Central, East).

Each of the 30 teams is announcing plans regarding attendance as the season progresses, something that depends on evolving local policies and restrictions. Therefore, some markets are able to have higher capacities than others. Stay tuned to MLB.com and each club’s site for more details, as policies continue to change throughout the year.

The 2021 All-Star Game remains scheduled for July 13. However, MLB announced on April 2 that it is relocating the game from Atlanta's Truist Park. Instead, it will be held at Denver's Coors Field for the first time since 1998. Also of note is that the MLB Draft is scheduled to be a part of the All-Star festivities for the first time. Information regarding All-Star Week in Denver, including tickets, can be found here.

The 2021 postseason schedule is not yet official. While the playoffs were expanded from 10 to 16 teams for 2020, that agreement was for one year only. The league and the players' union did not reach a new agreement regarding expanded playoffs for this year. In the absence of such a pact, the playoffs will once again feature five-team fields in both the AL and NL and begin with win-or-go-home Wild Card Games in both leagues.

The 2021 Minor League season
One effect of the pandemic was that the 2020 Minor League season was wiped out completely, as each team instead ran its own alternate training site in order to maintain a ready supply of roster replacements and provide hands-on instruction to some prized prospects.

The start of the Minor League season was again delayed in 2021, due to safety reasons, with MLB clubs once again operating alternate training sites to keep roster replacements ready. However, a restructured, streamlined version of the Minors finally got underway on May 4. Check MLB Pipeline for all the news about prospects and the Minors as the season progresses.

It's worth noting that things do look a bit different in the Minors in 2021, after MLB announced that each level will be a testing ground for rule changes. The goal of the program is to gauge the effect of the changes on issues such as the number of balls put in play, the pace and length of games and player safety. Among the rules: larger, less slippery bases (at Triple-A), restrictions on infield positioning (Double-A) and a 15-second pitch clock (in the Low-A West). The results of these changes will be studied to determine whether they merit consideration for future adoption in the Majors.