Head coach Dirk Koetter released a statement following Smith's firing:
"I have the utmost respect for Mike Smith as a man and as a football coach. These decisions are always difficult, but our top priority here is to ensure that we do everything possible to help this team succeed. As I have said in the past, the issues we have had as a team are never one person's fault. During good times, as well as the bad, it is a collective effort between the coaches and the players.
"We all understand that this is a result-based profession and our results to this point have not met our standards. I want to thank Mike for all the hard work and passion he has displayed here on a daily basis and I wish him well moving forward."
The Bucs have struggled immensely on defense, giving up 30 or more points in four of their first five games. During their three-game losing streak, they have allowed 37.3 points per contest.
They currently rank last in the NFL in points allowed (34.6 PPG), second-to-last in yards allowed (439.8 YPG) and last in pass yards allowed (355.6 YPG). They are tied for 28th in the NFL with nine sacks and have forced only five turnovers, tied for 28th in the league.
After Smith took over as defensive coordinator in 2016, the Bucs finished 23rd in yards allowed and 15th in points. They dipped to 32nd in yards allowed and 22nd in points allowed in 2017, and this season's disastrous start led to his ouster.
Smith's firing may also be a sign of desperation from Koetter, who is 16-21 as the head coach in Tampa and could find himself on the hot seat or even out of a job if the Buccaneers don't end their 10-season playoff drought in 2018.