The Vikings also made a change at cornerback because of injury, starting Marcus Sherels for the injured Chris Cook (hamstring).
They will have a week to consider making their quarterback change permanent and a week to analyze their secondary, as the Vikings returned home from London on Monday and started their bye week. Although it won't generate as much attention as the quarterback position, the cornerback decision may be just as important.
Cook is likely to return from his injury next week and resume his starting spot at right cornerback after a solid replacement job by Marcus Sherels over the last two weeks. The starting cornerback on the other side of the field may not be so cut-and-dried.
Josh Robinson has started all four games at left cornerback for the Vikings, taking over for veteran Antoine Winfield, who was released in a cost-savings move in March. But Robinson's performances leave a lot to be desired, according to statistics compiled by Pro Football Focus.
On Sunday in London, Robinson allowed 12 catches on 14 targets into his coverage area – and 91.9 percent of targets in his area this season (34 of 37) for 377 yards – according to PFF. That has played a big part in the Vikings having a pass defense ranked dead last in the NFL through four weeks.
In four weeks, the Vikings have given up 1,304 yards passing and generated 895. The 10 passing touchdowns allowed is also tied for worst with the New York Giants and Dallas Cowboys, and the 70 first downs allowed is second-worst in the league.
Robinson is hardly the only victim in the Vikings secondary, but he has given up 100 yards receiving in his coverage area, according to PFF, in back-to-back games to the Cleveland Browns and Pittsburgh Steelers.
He wasn't helped by a perfect first-quarter pass from QB Ben Roethlisberger to Emmanuel Sanders and over Robinson, going for 36 yards, tied for the longest pass play the Steelers had.
Vikings coach Leslie Frazier said last week he was hesitant to move first-round pick Xavier Rhodes to the right side of the field to cover for Cook's injury, so Rhodes continued to come into the game only when the Vikings needed five defensive backs. While Robinson played in all but two of the 79 defensive snaps, Rhodes was only used on 55 snaps.
Whether Rhodes supplants Robinson in a bye-week evaluation or not remains to be seen, but so far Robinson has been used far more but hasn't had much success defending the passes in his area.
"He did great. He's continued to improve, and it felt funny because he came to me on the sideline. He was telling me, hey, on the 42 lead, Troy (Polamalu), the safety is cramming in, and he's shooting right now," Peterson said of Webb. "So just trust me on being able to pin him in, you can get it outside. And sure enough, the next time we caught it, it happened exactly the way he was playing. So he's doing a good job to help me as well."
Tim Yotter is the publisher of Viking Update. Follow Viking Update on Twitter and discuss this story on our subscriber message board.