Usually, NFL teams don't keep covering the spread week after week. Not even for three weeks.

We're only three weeks into the NFL season, and only three teams haven't lost against the spread, according to Covers.com's standings. The three teams that have not let down bettors this season: Carolina Panthers, Denver Broncos and Dallas Cowboys.

The Panthers and Broncos are interesting cases. They've both looked good. They've also both beat the lowly New York Jets. The Broncos' three opponents are a combined 0-9. At least the Panthers have one quality win, against the New Orleans Saints. Both teams do pass the eye test and you can talk yourself into them being profitable going forward. But we do need to see what happens when they're facing teams tougher than the Jets, Jaguars or Texans.

But how about those Cowboys?

We can't chalk up the Cowboys' 3-0 start against the spread to a soft schedule. They covered at the Tampa Bay Buccaneers and Los Angeles Chargers, and the win against the Chargers has aged nicely. They blasted the Philadelphia Eagles on Monday night. The Eagles might not be very good, but the Cowboys never made bettors sweat.

One of the undefeated teams against the spread won't remain on that list past Week 4. The Panthers face the Cowboys in a suddenly intriguing NFC matchup. The Cowboys are 5-point favorites at BetMGM. That line moved from -4 to -5 after the Cowboys blew out the Eagles.

The Cowboys aren't going 1972 Dolphins against the spread this season. But they're the one team that is exceeding expectations most this season, and doing it against a legit schedule. That's worth noting.

OK, who are the winless teams against the spread?

It's pretty hard to go winless against the spread too, even after three weeks.

There are only four teams remaining who haven't covered a spread. That list of shame is the Jets, Jaguars, Washington Football team and ... the Kansas City Chiefs? The Chiefs' truly weird cold streak against the spread continued last week when they lost straight up as 7-point favorites to the Los Angeles Chargers. They've still just covered one spread since last Nov. 1. After the Eagles flopped on Monday night, the Chiefs went from 6-point favorites in Week 4 at Philadelphia to -7.5. Do you trust them?

If you like an underdog, take the moneyline

Getting points is nice, but most times if that NFL underdog you like covers, they win too.

That was mostly the case in Week 3. Of the nine underdogs that covered in Week 3, seven won straight up. The two that didn't were the Miami Dolphins and the Detroit Lions, who would have won straight up if not for a kind crossbar to the Baltimore Ravens on a 66-yard field goal.

If you believe in an underdog there's always some security in taking the points, but it's generally going to be more profitable to make moneyline bets.

Underdogs and road teams are still doing pretty good

As my colleague Minty Bets pointed out, underdogs have been the way to go so far this season. Underdogs have won each week, covering 11 times in Week 1, and nine times each in Weeks 2 and 3. That makes sense in a parity-driven NFL. It will also presumably start to even out at some point.

Home-field advantage still doesn't matter much. Home teams went 8-8 straight up and against the spread in Week 3. It's getting harder to figure out how many points to assign for home field, but the answer is probably fewer than we have been this season.