FOXBOROUGH — The Patriots beat the Texans by 18 points, covered a ridiculous 16-point spread, and won a playoff game behind an electrifying, record-setting performance from Dion Lewis.

So why is every Patriots fan pacing nervously about next Sunday’s AFC Championship game?

Because Saturday night’s 34-16 win was an ugly one for the Patriots offense. The Texans exposed a couple of significant flaws in the Patriots’ arsenal, providing the blueprint to beat them to any team that has even a marginal quarterback.

“Just very inconsistent for us, all the way around,’’ Tom Brady said after compiling the worst completion percentage of his postseason career (47.4 percent). “Whoever we play next week is going be a great football team, and we’re going to have to play better than we played tonight on offense.’’

Thankfully, the Texans are quarterbacked by Brock Osweiler, who didn’t disappoint with three interceptions and an inability to punch the ball into the end zone.

But the Patriots, now winners of eight straight games, are hardly invincible. With two interceptions from Brady and three lost turnovers overall, the Patriots looked like the Patriots from the end of the 2015 season, when they were uncharacteristically sloppy in game planning and execution and petered out in the AFC Championship game.

“If we want to keep winning and move on, we can’t play like that,’’ said receiver Julian Edelman (eight catches for 137 yards).

To be fair, the Texans have a solid defense — ranked No. 1 in yards and No. 11 in points allowed entering the game. They have two excellent young pass rushers in Jadeveon Clowney and Whitney Mercilus, a competitive secondary, and a coordinator in Romeo Crennel who knows how to attack Brady and the Patriots.

But if Saturday night’s game proved anything, it’s that Patriots fans shouldn’t book their tickets to Super Bowl LI just yet. Maybe the Patriots can’t just flip the switch and turn into a dominant offensive force, like we usually assume. Maybe they really do miss Rob Gronkowski, and we just didn’t notice because the Patriots haven’t really played anyone this year (not one game against a quarterback that finished in the top 10 in passer rating). No offense to Martellus Bennett (one catch for 4 yards on four targets, with two drops), but he’s no Gronk.

And if the Texans can put a scare into the Patriots — who were playing in the friendly confines of Gillette Stadium, no less — then the Steelers or Chiefs certainly can give the Patriots a run next Sunday. The Patriots would have lost Saturday night to a decent quarterback.

“It just, you know, doesn’t feel great, because you know we worked pretty hard to play a lot better than we played,’’ Brady said.

What did the Texans do to make Brady and the Patriots look pedestrian?

■ They made the Patriots one-dimensional on offense. The final stats say the Patriots rushed 27 times for 98 yards and a touchdown, but the run game wasn’t nearly that effective. Lewis rushed 13 times for 41 yards and LeGarrette Blount had just seven rushes for 13 yards before ripping off an 18-yarder at the end.

The Texans dominated the Patriots up front and took away any threat of the run, and the passing game struggled to connect without the threat of play-action. The Patriots needed some razzle-dazzle at the end of the game — an end-around to Edelman — just to move the ball and run out the clock.

■ They compressed the field and forced Brady to take deep shots. Brady’s deep ball is significantly better, but it’s still not the best part of his game. The Patriots would still prefer to move the football with rhythm passes, catch-and-runs, and Brady getting the ball out quickly. Instead, the Patriots’ best plays were the chuck-and-duck offense, in which Chris Hogan (45-yard catch) and Edelman (48-yarder and a missed push-off penalty) somehow came down with the football.

“A couple prayers,’’ Bill Belichick called them.

Brady deserves credit for completing five passes of at least 25 yards, and two more of 20-plus yards. He got his 287 passing yards on just 18 completions (15.9 yards per reception). But that’s not a high-percentage offense that the Patriots will want to rely on week-to-week.

“It was one of those nights where we really never got into a rhythm on offense,’’ Brady said. “They were kind of covering those shorter zones. We had more chances to take advantage of some down the field that we didn’t come up with.’’

■ They attacked the interior of the Patriots’ offensive line. The weaknesses of the line are rookie left guard Joe Thuney and second-year center David Andrews, and the Patriots’ inability to handle the Texans’ stunts and blitzes up the middle was the most disconcerting aspect of Saturday’s game. Clowney and Mercilus attacked Brady up the middle, not off the edge, and combined for five QB hits and a sack. Overall Brady was hit eight times by the Texans, taking several big shots (particularly from Clowney) and getting rattled in the pocket. Brady’s accuracy was notably off, as evidenced by throws behind Edelman and Bennett that he usually makes.

“I think we were prepared for it — we just didn’t do a great job of executing,’’ Brady said of the inside pressure.

■ They forced uncharacteristic mistakes. Brady threw two interceptions, matching his total from the regular season. His timing with new receiver Michael Floyd was way off, resulting in one interception and nearly another. Brady never saw linebacker Benardrick McKinney jump into his passing lane on his second interception. The Patriots fumbled twice, losing one.

Brady took one sack to knock the Patriots out of field goal range, and a Floyd penalty knocked them out of field goal range a second time.

The Texans stuffed the Patriots on the goal line, stopping them on two straight plays from the 1. The Patriots also punted three times in Houston territory, and blew the double-score opportunity at the end of the first half and beginning of the second.

On top of it all, the Patriots are a little banged up heading into Sunday’s game. Malcolm Mitchell missed the game with a knee injury, Danny Amendola is coming back slowly from an ankle injury, Hogan left the game with a quad injury, and Bennett keeps suffering nicks and bruises each week.

Fortunately, Lewis is an absolute stud (his two fumbles aside), James White is a tough matchup for any linebacker, and Edelman is tough to slow down.

But if you’re feeling confident about the Patriots’ chances next week in the AFC Championship game, well, you weren’t paying attention Saturday night.

“We’re going to have to play better, coach better than we did tonight,’’ Belichick said, “or there won’t be much left in our season.’’

Ben Volin can be reached at ben.volin@globe.com. Follow him on Twitter @BenVolin