EDEN PRAIRIE, Minn. -- On Thursday, when the Vikings are schedule to interview Cincinnati Bengals offensive coordinator Jay Gruden, it will have been 10 days since the team fired Leslie Frazier. At that juncture of their coaching search, here's what we know so far:

• The Vikings interviewed Seattle offensive coordinator Darrell Bevell and Seahawks defensive coordinator Dan Quinn over the weekend. They talked to Arizona Cardinals defensive coordinator Todd Bowles on Monday and Cleveland Browns defensive coordinator Ray Horton on Tuesday. They interviewed Bengals defensive coordinator Mike Zimmer on Wednesday.

• They are scheduled to interview Gruden on Thursday.

• They have requested interviews with San Francisco 49ers offensive coordinator Greg Roman, San Diego Chargers offensive coordinator Ken Whisenhunt, Denver Broncos offensive coordinator Adam Gase and Broncos defensive coordinator Jack Del Rio.

That means as of Thursday, the Vikings will have talked to six coordinators in the last six days, with four more still on the schedule. There could be other candidates they've talked to, but given what general manager Rick Spielman said last week -- that each interview is likely to last six to eight hours -- it's tough to imagine the Vikings have done more formal interviews than the ones mentioned so far.

A couple of themes emerge from this list, as it's currently constituted:

• The 10 names on this list are all current coordinators. Eight of the 10 have never been full-time NFL head coaches. Of those eight, one (Bowles) has been an interim head coach. After firing Frazier, Spielman talked about having researched 13 categories where head coaches come from, concluding that none was more successful than another. The majority of the list so far, though, is made up of coordinators with no prior head coaching experience -- which was the same category Frazier came from before he got the Vikings' interim job and then became head coach. Four of the eight coaches hired last year were previously coordinators, and one of those four (Bruce Arians) had been an interim coach. In 2012, coordinators made up three of the NFL's seven coaching hires, and all of them were first-time coaches. It's been a popular cradle for head coaches, but based on what we know so far, Spielman's search has been more focused than it has been diverse.

• We talked about this last week, but I think there's a real possibility the Vikings could bring in a coach who wants to run a 3-4 defense, and the coaches they've either talked to or expressed interest in so far would corroborate that theory. Quinn runs a 3-4/4-3 hybrid in Seattle and ran a 3-4 defense at the University of Florida. Bowles and Horton run 3-4 defense. Whisenhunt used a 3-4 when he was Arizona's head coach, and Roman's current team (the 49ers) uses one. If you're keeping score, based on the candidates we know about, the Vikings have split their time talking to or expressing interest in coaches from 3-4 and 4-3 teams. At the very least, it's an idea they're considering.

• The Vikings are one of five teams still looking for a head coach, but they're still not in any danger of missing Spielman's self-imposed deadline of the Senior Bowl. The GM said he will take two or three names to ownership for a final yes-or-no decision, and practices don't start at the Senior Bowl until Jan. 20. That might make it tough for Gase or Del Rio to enter the process if the Broncos wind up in the Super Bowl, but Spielman has also said the Vikings could wait until after the Senior Bowl if it took that long to find the right guy.

My guess is, we'll see things heat up in the next five to seven days. But barring an unexpected batch of names, it seems there are definite trends emerging in the Vikings' search.