Vikings: Robinson has broken sternum

EDEN PRAIRIE, Minn. -- The Minnesota Vikings' string of injuries in their secondary continued on Sunday; cornerback Josh Robinson will miss the next 4-6 weeks with a fractured sternum, coach Leslie Frazier said on Monday.

Frazier wasn't exactly sure when Robinson got injured on Sunday against the Seattle Seahawks, but it's possible that the second-year cornerback could miss the rest of the season. Rookie Xavier Rhodes will likely take Robinson's left cornerback spot in the base defense, with Marcus Sherels taking over for Robinson as the slot cornerback in the nickel.

Robinson has probably been the most-maligned cornerback on the Vikings' roster this season, though he's been far from the only problem with the secondary in the league's worst-scoring defense. He had started to improve in the last several weeks, but Pro Football Focus still has him ranked as the worst slot cornerback in the league.

Frazier also confirmed that center John Sullivan sustained a concussion on Sunday, and will have to go through the NFL's testing protocol before he can return to action. And though running back Adrian Peterson said after Sunday's game that his strained groin "was bothering me a lot," Frazier said it was too early to determine whether the Vikings might sit him down on Sunday against the Green Bay Packers and give him a chance to rest.

In more positive news, Frazier said wide receiver Greg Childs -- who tore the patellar tendons in both knees during training camp last year and has spent all season on the physically-unable-to-perform list -- will return to practice on Wednesday.