After the San Francisco 49ers took a 26-21 loss to the Jacksonville Jaguars on Sunday, things got heated between 49ers defensive coordinator Robert Saleh and Jags head coach Liam Coen.A small scuffle broke out while players shook hands, and Saleh and Coen were both walked away by their fellow coaches. Coen snapped at Saleh, and the Niners DC didn't hold back in his response."I'll f*ck your world up," Saleh said, per MLFootball on X. "You don't wanna f*ck with me. I will f*cking end your f*cking life."Tensions didn't escalate after Saleh's words, as everyone walked away.The 49ers' defense had a tough day at the office. The unit couldn't even record one sack, interception, or forced fumble on the day.They left their offense largely on the back foot, as quarterback Brock Purdy was forced to play from behind for most of the game.They now got a short break ahead of their Week 5 game. Traveling to Los Angeles, they'll take on the Rams in a divisional matchup next.Robert Saleh's 49ers defense struggled to get a grip on Liam Coen's offenseThe game started off on a stable note for the 49ers. They put up the only points of the first quarter, with a 26-yard field goal by Eddy Pineiro. However, things quickly spiraled out of control for them.Another Pineiro field goal in the second quarter wasn't nearly enough to keep up with the Jaguars' offense that caught fire. A rushing touchdown by Travis Etienne, a passing touchdown by Trevor Lawrence, and a field goal right before the half saw Jacksonville head to the locker room with a 17-6 lead.Brock Purdy finally found the end zone in the third quarter, with a short pass to running back Christian McCaffrey. But it was hardly enough to keep up with the nine points surrendered by Saleh's defense.While the defense finally found its footing in the fourth, Purdy's one touchdown pass to Jake Tonges wasn't enough to overcome the deficit. The Jaguars' defense held on for the 26-21 victory.