It’s too early to write off the Cowboys after one game, but there sure were a lot of red flags in their ugly, 28-17 home loss to the 49ers.

All of the concerns about the roster Jerry Jones constructed were on display, as Tony Romo threw three interceptions in his first full game since back surgery, the injury-ravaged defense allowed 316 yards and Dallas was penalized 10 times.

Romo, of course, is the biggest concern. He was never fleet to begin with, but he looked a lot older than 34 and it was obvious by the way he floated passes that all the injuries are starting to take a big toll on his performance.

And considering Romo threw just 10 interceptions in 15 starts last season, the trendline this year isn’t exactly going in a positive direction.

What was even more ominous is the Cowboys can’t get rid of Romo anytime soon, even if they wanted to. That’s because the recent extension Jones gave him would immediately cost Dallas a whopping $48 million in “dead” money under the salary cap.

As a result, Romo is untradeable and uncuttable. So, barring more injuries, Cowboys fans should resign themselves to Romo at quarterback for at least the next two seasons.

The Chiefs and Rams stink, too

The feel-good turnaround by the Chiefs under Andy Reid may have already run its course.

The wheels were already starting to fall off last season, when Kansas City lost six of its final eight games after a 9-0 start. The low point came in the playoffs, when the Chiefs somehow blew a 38-10 third-quarter lead over the Colts in the wild-card round.

Sunday’s 26-10 loss to the Titans at home often seemed like just a continuation of that hideous fourth quarter in Indianapolis last January. Alex Smith threw three interceptions in his first game since getting a huge contract extension, and their once-vaunted defense was picked apart by Jake Locker, of all people.

And to add injury to insult, two of their key defenders — linebacker Derrick Johnson and lineman Mike DeVito — suffered season-ending tears to their Achilles tendons.

Plus, look at the Chiefs’ next five games: at Denver, at Miami, New England, at San Francisco and at San Diego.

It looks like the bad old times returned to Kansas City in a hurry.

The Rams’ Jeff Fisher is an elite coach with an elite pass rush that should keep most games close, but he can’t win with backup quarterbacks.

Peyton’s still Peyton … are the Colts still the Colts?

It looks like Peyton Manning won’t rest until he sees the Seahawks again in the Super Bowl. John Elway replaced Eric Decker with Emmanuel Sanders and Peyton already loves him. Montee Ball will make them forget Knowshon Moreno. More on Julius Thomas later.

The AFC South is wide open in the wake of Monday’s news that Colts defensive end Robert Mathis suffered a season-ending tear of his Achilles tendon in a workout last week.

Mathis was in the midst of a four-game NFL suspension for PEDs, but the Colts now will have to do without the heart of their defense for a lot longer than expected.

Granted, Manning skews the example, but Sunday night’s 31-24 loss to the Broncos illustrated the problems the Colts face without the player who led the NFL with 19 1/2 sacks last season.

Indy’s pass rush was mostly non-existent (Manning was sacked just once), and Manning barely broke a sweat early while throwing three TDs without an interception.

The Colts stiffened late and had a chance to force overtime, and having Andrew Luck means they will be in every game they play. But this is a team that looks like it could be playing from behind against every team with a capable quarterback, and that’s no way to reach the Super Bowl.

No lead is safe in this league

Raise your hand if you thought the Jaguars — yes, even the Jaguars — would blow a 17-0 halftime lead to the Eagles and lose 34-17 on a day when Nick Foles, who committed four turnovers in 2013, lost two fumbles on strip sacks and threw a pick and had to notice Mark Sanchez warming up in the bullpen.

Raise your hand if you thought the Brian Hoyer Browns, thanks to a no-huddle attack, would storm back from a 27-3 deficit in Pittsburgh to tie the Steelers and cover the point spread in a 30-27 loss that will keep Johnny Cleveland on the sidelines. Did Mike Tomlin hand out the Steelers playbook at halftime or something?

Raise your hand if you thought Matt Ryan would throw for a franchise-record 448 yards and 3 TDs against Rob Ryan’s defense and overcome a 20-7 deficit against Drew Brees for a 37-34 victory over the Saints at the Georgia Dome.

Raise your hand if you thought the Ravens would storm back from a 15-0 deficit against the Bengals to take a 16-15 lead before A.J. Green’s 77-yard TD catch denied them.

Raise your hand if you thought Luck and the Colts would storm back from a 24-0 deficit and make Peyton and the Broncos sweat a 31-24 deficit at Mile High. OK, I see a couple of hands here.

The tight end is the QB’s best friend

Ask Manning what he thinks of Julius Thomas (3 TDs) as a red-zone weapon. Ask Colin Kaepernick about Vernon Davis (2 TDs).

No fewer than nine other tight ends caught a touchdown pass on Sunday: Rob Gronkowski (Patriots), Levine Toilolo (Falcons), Greg Olsen (Panthers), Dwayne Allen (Colts), Kyle Rudolph (Vikings), Zach Ertz (Eagles), Martellus Bennett (Bears), Delanie Walker (Titans) and Anthony Fasano (Chiefs). No crossbar dunks for Jimmy Graham, however.

RG3 doesn’t scare anyone anymore

Except for maybe Jay Gruden, who concocted a savvy game plan that consisted of getting the ball out of his quarterback’s hands with short passes so J.J. Watt wouldn’t wreck the game. RG3 hasn’t looked comfortable as a pocket passer in the West Coast offense and completing 29-of-37 passes is nice, but not if you can’t get your team in the end zone. RG3 attempted an ill-advised handoff to Alfred Morris after his center stepped on his foot and fumbled away a red-zone opportunity. The bloom sure is off the rose, RG3 a far cry from the dynamic player who captivated the imagination as a rookie two seasons ago. The drumbeat for backup Kirk Cousins will only grow louder.

By crook or by rook

When he returns in Week 2, Cam Newton will love throwing to towering No. 1 pick Kelvin Benjamin (6-92-1 TD).

Drew Brees is excited about speedy No. 1 pick Brandin Cooks (7-77-1 TD).

The biggest surprise had to be undrafted Jaguar Allen Hurns (4-110-2TDs).

The Bills’ Sammy Watkins, the first receiver drafted, was a quiet 3-31. The Bucs’ Mike Evans, the second receiver drafted, was 5-37.

The Browns’ Terrance West (16-100 rushing) was the best of the rookie running backs, while teammate Isaiah Crowell scored two TDs after Ben Tate (knee) left in the first half.

Extra points

• Adrian Peterson has himself an electrifying sidekick in Cordarrelle Patterson, who is a Lethal Weapon catching and running the ball. Mike Zimmer gets this vote for best rookie head coach. Once Teddy Bridgewater is deemed ready, this has the makings of a surprise team. Hang on, All Day, keep hope alive.

• The so-called Monsters of the Midway were exposed as too soft in surrendering 193 rushing yards to the visiting Bills. That’s Bupkis, not Butkus. More like Da Bares.

• A five-field-goal extravaganza for the Bengals’ Mike Nugent. A game-tying 51-yard field goal by Matt Bryant followed by a 52-yard game-winner for the Falcons. A 41-yard game-winner by the Steelers’ Shaun Suisham. A 27-yard overtime Bills game-winner by Dan Carpenter. Four field goals by the Titans’ Ryan Succop. Four field goals by the Dolphins’ Caleb Sturgis. But the gold medal winner is Antonio Brown for a premature hurdle that resulted in a right foot to the face of Browns punter Spencer Lanning.

• On third-and-10 from the Cincinnati 15-yard line with eight seconds left in the first half, Flacco, who would throw a ridiculous 62 times, took a sack as time ran out. “That was probably the stupidest play I’ve ever made in football,” he said.

• Meniscus is the bet for Jadeveon Clowney. So much for Defensive Rookie of the Year honors. A shame. But Watt will survive.