The mystery of who the Patriots starting quarterback will be in Week 4 plods on.

CBSSports.com NFL insider Jason La Canfora reports that the team has yet to determine who will start at quarterback against the Bills on Sunday. The decision could hinge on how each player performs during pregame workouts, per La Canfora.

Early Saturday, Boston radio station WEEI reported that New England will be going with Jimmy Garoppolo on Sunday. If Garoppolo does play, he'd be returning to the game action just 10 days after suffering a sprained AC joint in his shoulder during the Pats' 31-24 win over the Dolphins in Week 2. Although Jacoby Brissett started in Week 3, he injured his thumb, which left his availability in question for this week.

Both players are listed as questionable for Sunday's game.

Patriots coach Bill Belichick doesn't offer injury updates on his players, so the only one we got this week on Garoppolo came from the quarterback himself.

During his media session on Wednesday, Garoppolo was asked how his shoulder felt.

"It's coming along. Day-by-day right now, trying to get to the best of my ability on Sunday," Garoppolo said, via WEEI.com. "Just trying to get better every day, That's all that you can ask for with this. We're just taking it day-by-day, really."

I think what Jimmy is trying to tell us is that he's taking it day-by-day. Garoppolo's shoulder has been healthy enough this week that he's seemingly been able to throw without much pain.

Of course, since this is the Patriots we're talking about, nothing is set in stone as far as the quarterback position goes until either Garoppolo or Brissett actually takes the field on Sunday.

The Patriots have been so secretive about who their starting quarterback will be this week that it's actually become a running joke at Rex Ryan's press conferences. Ryan was asked on Monday if he thought Belichick would name a starter or keep it a secret.

"I expect them immediately to tell us," Ryan joked. "As soon as they tell us, we'll be like, 'Yeah, ok.' Nobody would believe it anyway, Nah, I don't know. We're not going to find out until kickoff."

Two days later, Ryan said he thought he knew who the Patriots would be starting, but he didn't want to say the player's name out loud because he didn't want to jinx himself.

"If I'm wrong, it'll be like, 'Oh, he wasn't right. What a shock,'" Ryan said, via ESPN.com.

Ryan's been so obsessed with finding out who the Patriots quarterback will be that he actually took off his coaching hat this week and put on his reporter hat. During Julian Edelman's teleconference with Buffalo media on Wednesday, Ryan posed as a reporter and asked Edelman if he would be playing quarterback at all against Buffalo.

After Sunday's game, it will be a lot easier to figure out who the Patriots starting quarterback will be. Tom Brady is eligible to return on Monday.