The spring transfer window lasts just 15 days and is not nearly as active as the 45-day period that comes after the college football season — unless you're Colorado.

Coach Deion Sanders' team has added 20 transfers since the portal window opened April 15. Among the most notable additions were former Houston running back Alton McCaskill, former five-star recruit and Washington linebacker Sav'ell Smalls and a handful of ex-Florida State players.

The Buffaloes are up to 48 transfers overall, according to 247 Sports, and have room for more. They were the most frequent portal shoppers this spring — but not necessarily the biggest winners as other schools went for quality over quantity.

SOUTHERN CALIFORNIA

The rarest commodity in the portal are talented linemen. The Trojans landed one on each side of the ball while most of the attention in the Pac-12 was on Colorado.

Bear Alexander, 6-foot-3 and 305 pounds, is a former top-100 recruit who played effectively in a reserve role for national champion Georgia last year.

Emmanuel Pregnon, 6-6, 318, was a no-star prospect out of Denver and hardly played in his first two seasons at Wyoming before emerging as one of the best guards in the Mountain West last year.

USC also added Alabama defensive back Tre’Quon Fegans, another former blue-chipper, to a defense that definitely needed some upgrades.

ALABAMA

The Crimson Tide made headlines when it brought in former Notre Dame quarterback Tyler Buchner to compete for the starting job after none of its highly touted incumbents asserted themselves this spring. Buchner played for new Alabama offensive coordinator Tommy Rees in South Bend, Indiana.

Nick Saban also decided the Tide was light in the secondary and added two Group of Five defensive backs in UAB safety Jaylen Key and Louisiana cornerback Trey Amos.

AUBURN

New coach Hugh Freeze has some building to do with the Tigers, especially on an offense that had the worst passing game in the Southeastern Conference last season.

Enter former Michigan State quarterback Payton Thorne, who even in an inconsistent 2022 season threw more than twice as many touchdown passes (19) as Auburn's quarterbacks combined (nine).

At receiver, the spring window delivered former Ohio State four-star recruit Caleb Burton and Jyaire Shorter from North Texas to Auburn, which also got a recent commitment from Shane Hooks. He caught 64 passes for 748 yards and 10 touchdowns at for Sanders' Jackson State team last year.

Linebackers Jalen McLeod from Appalachian State and Shorter's North Texas teammate, Larry Nixon III, were brought in to reinforce the defense. Offensive lineman Jaden Muskrat was a starter for new offensive coordinator Philip Montgomery at Tulsa.

MIAMI

The Hurricanes needed another running back and lured Ajay Allen from Nebraska to Coral Gables, Florida. Allen flashed intriguing potential and speed in four games before getting hurt in 2023.

Cornerbacks Jadais Richard, a veteran from Vanderbilt and Jaden Davis from Oklahoma both have a chance to start, and 6-foot-7 defensive lineman Jason Campbell has interesting upside.

NORTHWESTERN

Elite academic schools can be limited when it comes to bringing in transfers. The Wildcats landed two in the last month that coach Pat Fitzgerald hopes can inject some life into an offense that has lacked punch the last two seasons.

Ben Bryant comes over from Cincinnati to try to fill a hole at quarterback. He was solid as a starter for the Bearcats last year, with 21 touchdown passes and seven interceptions.

Former Michigan receiver A.J. Henning has been one of the most dangerous kick returners in the Big Ten the last two seasons.

LOUISVILLE

Like a lot of first-year coaches, Jeff Brohm is leaning into the portal to flip the roster. The new Cardinals coach has 23 transfers overall, with several key additions in the last month.

Former four-star quarterback Brady Allen and offensive lineman Eric Miller followed Brohm down from Purdue.

Cornerbacks Marcus Washington (Georgia) and Storm Duck (Penn State via North Carolina) were added to the secondary, and offensive lineman Lance Robinson comes over from Houston.

___

Follow Ralph D. Russo at https://twitter.com/ralphDrussoAP and listen at http://www.appodcasts.com

___

AP college football: https://apnews.com/hub/college-football and https://twitter.com/ap_top25