September is officially here and that means rosters are expanding across Major League Baseball.The final month of the 2026 regular season has arrived and that means that from here on out, clubs will be able to have 28 players on the active roster, instead of 26. For the Red Sox, Isiah Kiner-Falefa has been the obvious name to watch over the last week, or so. On Tuesday, the Red Sox announced that Kiner-Falefa has been activated off the Injured List and brought back up to Boston. That's not all, though. Boston announced that 22-year-old Jedixson Páez has been selected to the big league roster and that he will make his Boston debut on Tuesday night against the Seattle Mariners. To make room on the roster, Boston placed Eduardo Rivera on the 60-day Injured List and designated Brett Harris for assignment as a result."Selected right-handed pitcher Jedixson Páez to the Major League roster from Triple-A Worcester," the Red Sox announced. "He will start tonight's game against the Seattle Mariners. Reinstated infielder Isiah Kiner-Falefa from the 60-day Injured List. Recalled left-handed pitcher Eduardo Rivera from Triple-A Worcester and placed him on the 60-day Injured List with a lumbar strain. Designated infielder Brett Harris for assignment."The #RedSox today announced the following roster moves: pic.twitter.com/vis1I9eFGm— Red Sox (@RedSox) September 1, 2026Isiah Kiner-Falefa ReturnJun 18, 2026; Boston, Massachusetts, USA; Boston Red Sox shortstop Isiah Kiner-Falefa (2) celebrates his home run against the Toronto Blue Jays during the eighth inning at Fenway Park. Mandatory Credit: Eric Canha-Imagn Images | IMAGN IMAGES via Reuters ConnectKiner-Falefa is the exact type of veteran you want on a team for a playoff push. He's been around the block, to say the least. He was a member of the Toronto Blue Jays last year as they made a run to the World Series, for example. He's a talented player in his own right and he was batting .277 before landing on the Injured List. More importantly, though, he's going to bring roster flexibility and veteran leadership to a young roster down the stretch. Jedixson Páez Boston DebutMar 31, 2026; Miami, Florida, USA; Chicago White Sox pitcher Jedixson Paez (63) delivers a pitch against the Miami Marlins during the eighth inning at loanDepot Park. Mandatory Credit: Sam Navarro-Imagn Images | IMAGN IMAGES via Reuters ConnectPáez was picked in the Rule 5 Draft by the Chicago White Sox and actually made his big league debut earlier in the campaign with them. He pitched in three games before being returned to Boston. He has made three starts with Triple-A Worcester this season and has a 2.92 ERA down there. Now, he's getting a chance to show Boston fans what he can do. Eduardo Rivera 60-Day Injured ListJul 17, 2026; Boston, Massachusetts, USA; Boston Red Sox pitcher Eduardo Rivera (99) pitches during the first inning against the Tampa Bay Rays at Fenway Park. Mandatory Credit: Bob DeChiara-Imagn Images | IMAGN IMAGES via Reuters ConnectRivera's season is over, but it was a successful one. He made his big league debut and got into four games, including three starts for Boston. Most of his season was spent with Triple-A Worcester, where he logged a 2.96 ERA in 24 appearances. The 23-year-old has a bright future. Brett Harris DFA'd Sep 28, 2025; West Sacramento, California, USA; Athletics third baseman Brett Harris (11) throws to first for an out against the Kansas City Royals during the fifth inning at Sutter Health Park. Mandatory Credit: Dennis Lee-Imagn Images | IMAGN IMAGES via Reuters ConnectHarris is a roster casualty here. The three-year MLB veteran played in just one game for the Red Sox in the majors earlier in the season. His 2026 season has been split between the Red Sox's organization and the Athletics' organization. Now, he's being designated for assignment and clubs will have a chance to claim him.Add us as a preferred source on GoogleFollow