Before donning his white lab coat for a long day at Gaffney Chicago Medical Center, Donnell played Tommy Merlyn on The CW series "Arrow." According to his IMDb page, he still played the role during and after his tenure on "Chicago Med." He appeared in more than 25 episodes of "Arrow" between 2012 and 2020, with his last appearance happening on the series' final episode, "Fadeout." Tommy is the best friend and, later, an antagonist to Oliver Queen (Stephen Amell). He even takes up the moniker of "Dark Archer" for a spell.
Besides acting on "Arrow," Donnell has also appeared in two TV movies since he left "Chicago Med." His IMDb page reports he first showed up in the 2020 romance "Love on Iceland," which stars Donnell, Kaitlin Doubleday, and Preston Sadleir. This direct-to-TV movie also aired on the Hallmark Channel. In typical Hallmark fashion, the story follows a renewed romance between two ex-lovers as they tour Iceland. Donnell's next TV movie is also another product of Hallmark: 2021's "To Catch A Spy" (via IMDb). Unlike the previously Hallmark project, this feature is predominantly a thriller-mystery that involves the falling death of an individual at a hotel in Malta and the people trying to solve the case.
Luckily for fans of Donnell's work, he has an upcoming television show soon on the horizon called "Irreverent," which also stars P.J. Byrne, Robert Rabiah, Wayne Blair, and Kylie Bracknell. The show is set to premiere on June 1 on Peacock (via IMDb). Donnell plays the role of Mack on this future show, and the character is a former go-between for Chicago-based gangs, but he retreats to Australia and takes up a cover as a reverend (via Deadline).