From 2003 to 2004, Alston attempted to break into the National Football League (NFL), spending time with three different teams in the preseason or as a practice squad player.
In the 93rd Grey Cup, Alston sacked the opposing quarterback in overtime, leading to a scoreless drive for the Montreal Alouettes and a 38–35 win for the Eskimos.
[9][10] Alston made a tackle for a loss on the final play of a post-season game against the Virginia State Trojans, resulting in the Bulldogs receiving the CIAA East Division title.
[14] The Atlanta Falcons signed Alston immediately after the end of the 2003 season and allocated him to the Amsterdam Admirals of NFL Europe.
He found some success with the Admirals, being named the NFL Europe Defensive Player of the Week in May after recording four tackles and two sacks in a single game.
[16] Alston competed for a spot on the Falcons roster in training camp, but he was cut from the team in early September before the start of the 2004 regular season.
[24][25] Alston returned to the lineup and made his first career start in October, when he forced a fumble from Toronto Argonauts running back John Avery.
[4][27][28][29] Alston won "Best Lineman" honors in the West final win against the BC Lions, where he recorded seven tackles, a sack, and a pass knockdown.
[4] In August, Alston sacked Saskatchewan Roughriders quarterback Kerry Joseph on their final drive, resulting in a 24–18 win.
[40] In August, Alston replaced Adam Braidwood as the starting defensive end, but he was injured with a hip pointer in his first game in that role.
Head coach Danny Maciocia cited Alston's history of injuries as a factor in his release from the team.
[46] In February 2008, Alston signed with the Kansas City Brigade of the Arena Football League, but he left the team later that same month.