What are MLB September call-ups? Explaining why many teams are promoting prospects and their playoff eligibility

Fans across the league may have noticed a flurry of players being promoted to the MLB from the minor leagues; these are known as the September call-ups.

Historically, teams have been able to promote as many players from their 40-man roster to the MLB to help their postseason pushes, but that has since changed.

"Word is Jasson Dominguez will indeed make his major-league debut this weekend. He was on my list of 14 prospects that I'm hoping to see in September:" - @CBSScottWhite

Now, the MLB's policy regarding September call-ups is a bit different than in previous seasons. For one, MLB rosters have moved from 25 to 26 players throughout the season, but during the month of September, the number of players jumps to 28.

However, the key bullet point is that teams must have 28 men on their MLB rosters, which explains the number of players being called up across the league. Now, this is exciting news for some, as they're granted their first taste of MLB action or a return after years away. Nevertheless, the new roster policies make it closer to ordinary roster moves than an exceptional wave of shakeups.

Among the veterans that we have already seen promoted to the MLB include Andrew Stevenson with the Minnesota Twins and Shane Greene with the Chicago Cubs. These players have been given the opportunity to return to the major leagues after some rocky years.

We have also seen many young players earning the opportunity to prove themselves at the MLB level. One of the September call-ups making their MLB debuts is Alexander Canario with the Chicago Cubs.

The 23-year-old from Monte Cristi, Dominican Republic, has been electric in August, producing a dazzling .305 batting average with seven home runs, 25 RBIs, and a pair of stolen bases.

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Are the players promoted during September call-ups eligible for postseason?

The short answer is yes; they are eligible. Players who are on the 40-man roster or on the 60-day IL from Aug. 1 are able to play for their respective teams come postseason time.

While there's an opportunity that these September call-ups are merely depth additions, there are examples throughout MLB history of such players emerging as stars.

"Viva El Birdos: Remembering J.D. Drew's 1998 September call-up, because somebody has to" - @CardsPulse

One of the most notable call-ups who proved his worth for his team is former slugger J.D. Drew when he was promoted by the St. Louis Cardinals in 1998. Through only 14 games following his promotion, he produced a .417 batting average with five home runs.