September 1 marks the date on which regular-season rosters expand from 25 to 40 in Major League Baseball. While the merit of that rule and its impact on games are a source of debate — MLB games tend to increase considerably in length in September as managers can more freely make pitching changes with deeper bullpens — the fact remains that there could be more than 100 players promoted to the big leagues today as the first wave of call-ups arrives.

Many September call-ups are players that have experience already under their belt. Journeyman big leaguers with exceptionally specific roles (e.g. pinch-running and defensive specialists) become a luxury that teams can now afford, and many teams will bring up a third catcher or additional bullpen arms for depth, even if a long-term MLB role isn’t likely for said players.

Some promotions, though, are more notable than others. Big league teams will often use the month of September to get a look at their top organizational prospects, and in some instances September can provide a potential audition for former stars seeking to reestablish themselves. (The Orioles, for instance, were reported last night to be bringing slugger Pedro Alvarez up from Triple-A for the season’s final month.)

All that said, here are some of this year’s more notable September promotions (we’ll update throughout the day as more moves are announced)…

• Four new youngsters are joining the Cardinals, the team announced. Outfielder Harrison Bader and infielder Alex Mejia were already on the 40-man, but the team has also gone ahead and added righty Sandy Alcantara and backstop Alberto Rosario. Alcantara is an interesting pitcher to keep an eye on, as he reputedly comes with a big arm and could contribute from the bullpen — though he’s still ironing things out as a starter after spending the year pitching to a 4.31 ERA at Double-A.
• The Indians announced that they’ve recalled top catching prospect Francisco Mejia from Double-A Akron and selected the contract of outfielder Greg Allen from Akron, thus adding him to the 40-man roster. The 21-year-old Mejia is commonly regarded as one of the top 25 prospects in all of Major League Baseball and was reportedly the would-be centerpiece to the Jonathan Lucroy trade that Lucroy vetoed in 2016. Allen, too, was set to be a part of that trade but has instead remained in the Indians organization and will now join Mejia in donning a big league jersey for the first time this month.
• Right-hander Fernando Salas will return to the Angels, who announced last night that his contract has been selected from Triple-A Salt Lake. Salas spent parts of three seasons as a useful bullpen arm for the Angels before a trade to the Mets last August. While he dominated for New York down the stretch, Salas was torched for a 6.00 ERA this year after re-signing with the Mets. He tossed three scoreless innings in Salt Lake City and will hope for a strong finish to bolster offseason interest.
• The Blue Jays, too, will be getting another look at an old friend. Outfielder Michael Saunders is joining the Jays as a September call-up, tweets MLB.com’s Greg Johns. While Saunders is merely looking to show well in his return to the Majors after struggling badly with the Phillies earlier this season, another outfielder is looking to carve out a long-term role in Toronto; trade acquisition Teoscar Hernandez is also on his way to the Majors, per Johns. The 24-year-old Hernandez was acquired in the Francisco Liriano swap and has posted a combined .265/.351/.490 batting line in 456 Triple-A plate appearances this season.
• The Mets are promoting right-handers Jacob Rhame and Jamie Callahan, tweets MLB.com’s Anthony DiComo. While neither reliever is considered to be among the game’s best prospects — they rank 23rd and 30th, respectively, on MLB.com’s list of the Mets’ top 30 prospects — both were recently acquired on the trade market. Rhame came to the Mets from the Dodgers as the return for Curtis Granderson, while Callahan arrived in Queens by way of the Addison Reed trade with the Red Sox. Both will be looking to make a strong impression as they seek to secure a long-term spot in the Mets’ bullpen.
• The Tigers are getting their first look at left-handed reliever Jairo Labourt, per a team announcement. The 23-year-old was acquired alongside Daniel Norris and Matt Boyd in exchange fo David Price back in 2015. He’s turned in an excellent 2.17 ERA across three minor league levels this season and averaged better than 10 strikeouts per nine innings, albeit with some shaky control (4.5 BB/9).