Kammala jumla mai zuwa: A ranar 26 ga Fabrairu, 2018, an yi musayar McDonagh (tare da J. T. Miller) zuwa Tampa Bay Lightning a musayar Libor Hájek, Brett Howden, Vladislav Namestnikov, zagaye na farko a cikin 2018 NHL Entry Draft, da kuma zagaye na biyu na zagaye na biyu a cikin
Zaben shiga NHL na 2019. Kasuwancin ya biyo bayan makonni na jita-jitar cinikin da wasikar ƙungiyar ta yi wa magoya bayan Rangers a ranar 8 ga Fabrairu, 2018, tana sanar da sake ginawa. A ranar 18 ga Afrilu, 2018, McDonagh ya taka leda a wasansa na 100 na NHL.