Tonkin signed a minor-league contract with Atlanta on Jan. 11.
Tonkin has thrown 146.1 innings at the highest level, posting a 4.43 ERA. The last of those came back in 2017, however. Since then, he's spent time pitching in Japan, Mexico and the independent Atlantic League, where he recorded an 0.53 ERA and a 21:5 K:BB last season in 17 innings as a member of the Long Island Ducks.