Largely due to a strong performance by Joseph, the Saskatchewan Roughriders built up a 27-15 lead over the Calgary Stampeders through three quarters.
The Stamps (14-2) then responded with 25 straight points in the fourth quarter to win 40-27. It was the fifth straight loss for the Riders (9-8) and the second in a row with Joseph at quarterback.
"We just lost momentum," said Joseph, who completed 21-of-37 passes for 322 yards and two touchdowns. "The game is on me. Three interceptions, that's on me."
After Calgary took a 30-27 lead early in the fourth the Riders still had a chance to answer back, but Jamar Wall picked off an errant Joseph pass and ran it back 50 yards for a back-breaking touchdown.
"I've got to see the field better and I can't turn the ball over," said Joseph, who subsequently threw two more interceptions to Brandon Smith and another to Wall in the end zone late in the game. "They brought me in here to lift this team up. Two weeks in a row, I turned the ball over and let these guys down. It's just inexcusable."
Saskatchewan coach Corey Chamblin wouldn't go so far as pinning the loss on his veteran quarterback.
"Kerry's doing a phenomenal job," Chamblin said. "He's a little tough on himself. He threw some picks at the end. That was just part of where we were towards the end of the fourth quarter. I don't want to say we ran out of gas, but the Stampeders, they are a strong team.
"It showed where they are and where we are. I think we know just as a whole, we have a little bit more to go to be able to defeat a team like that."
Receiver Korey Williams, who had three catches for 55 yards, also refused to put all the blame on Joseph.
"It's never on one guy," Williams said. "We have to block, we have to catch the ball, he has to throw the ball. It's a whole bunch of things. You can never just say one guy messed up. We just have to continuously move forward and build off the opportunities that we have."
The Riders now have a bye-week before they host the Edmonton Eskimos in Regina on Nov. 8 for their final regular season game.
"We've got to try to stay positive," Joseph said. "We've still got a football game to play. We've got one more and then we've got the playoffs. It's not like we're out of the playoffs. We've got to find a way to win. I've got to find a way to be better."
Williams agreed that the Riders have to try to remain positive despite the fact they're in the midst of a five-game losing skid.
"We've been building positives for a while," he said. "It's just that we have to learn to win games when we have the opportunity to win them. It's as simple as that."
Despite the setback to the Stamps, Chamblin said he saw some positives that the Riders can build on heading into the post-season.
"This team is growing," Chamblin said. "We're young in some areas and I'm seeing guys grow through experience. We're going to have a chance. I think over the next couple of weeks this team will grow. At the right time, I think we'll be ready."