Brock Purdy has now seen significant action in four games for the 49ers, throwing two touchdowns and completing at least 65% of his passes in each. The 49ers have won all four games by at least eight points, with the average margin of victory 17.25 points while scoring an average of 31.5 points per game. The 49ers scored 30-plus points in three of their first 11 games, then three more after Purdy got involved over the last four weeks. Purdy's latest 37-20 gem came against a Commanders team that hadn't surrendered more than 21 points since Week 4 and more than 25 points just once prior.

After Jimmy Garoppolo's injury, it was necessary to downgrade the 49ers' power rating with a rookie who was the last pick of this year's draft taking over the reins. Now, it appears Purdy hasn't just picked up where Garoppolo left off, but maybe even raised San Francisco's ceiling in the process. That's why I've bumped the 49ers up significantly in my power ratings, putting them above the Cowboys as the fourth-best team in the league for this week behind the top three AFC juggernauts. (Where's Philadelphia? With Jalen Hurts' health uncertain, they remain a tier below the top teams in my power ratings, which only reflect the strength of a team in the current week.)

Another team that gets a lift in the ratings is the Jets, who I restored to being 1.5 points above average with Mike White returning this week. That may seem a little high for a quarterback of his caliber, but this Jets defense has proven to be elite, and you can see above with the Purdy analysis where this team might rank if I had more confidence in the offense. For now, the Jets remain level with the Chargers and Jaguars, which still makes them a top-10 team in my power ratings for this week.

What are power ratings? Well, anyone who has followed football (or really any sport) for any length of time has encountered a power rankings list that projects teams from best to worst. Where power ratings for NFL betting differs is that you're affixing a point total to each team that tells you how much better or worse it is from an average team. For example, if you think the Packers are the midpoint of the league, their power rating would be a zero. If you think the Vikings are a little bit better, you might make them a +1. The Chargers may be another step above and worth a +2 rating. Going the other way, you may think the Raiders are a -1 or -2 team (or even worse).

After you've rated all 32 teams in this fashion, you can take the difference between two teams in a scheduled matchup to determine what the line would be on a neutral field. In our example above, we'd say the Chargers should be favored by two points against the Packers on a neutral field. Then you add in home field advantage, which for a long time was considered three points as a standard but is actually lower on average in this era of football. I actually determine unique home field advantage totals for each team based on data from the last five years, and you can find my breakdown of this year's home-field advantage ratings here. I updated the HFA numbers of a few teams in my weekly workbook after six weeks and again after 12 weeks with a better understanding of which teams are good and bad, and which fan bases are likely to be more engaged than previously anticipated.

I've dived into each Week 17 game and evaluated my Week 17 power ratings to see what needed to be adjusted. I've also shared analysis of the most extreme differences between my projected lines and the market, as well as done the math to project the spread of every game based on my power ratings.

Which lines are several points off their power rating projections for Week 17? And which teams are being undervalued by the market? ... Join SportsLine right now to see Week 17 power ratings from the expert who's 445-378-24 on ATS picks from 2017-21, returning $2,542 to $100 players!