Allen made his Colts practice debut in Thursday's joint practice with the Falcons, Noah Compton of SI.com reports.
Allen wasn't expected to participate in team drills after signing earlier this week, but he took four reps in 11-on-11 work against Atlanta's defense. "He's been productive every single year he's been in the league. So obviously, we want him to be productive again this year," coach Shane Steichen said Wednesday. "He'll come in - obviously, he's been in this system. He'll pick it up quickly, but he'll play outside. He'll play inside. We'll move all our guys around." Allen is expected to be a mainstay in three-wide sets for Indianapolis and could even push Josh Downs out of two-wide sets once Alec Pierce (ankle) is ready to go. Should he emerge as a high-volume target in his new locale, Allen's addition has the potential to negatively affect all three of Pierce, Downs and Tyler Warren's fantasy impact.