Happy now?

After all the hand-wringing and teeth gnashing among New England Patriots fans through the first four weeks of the season, the mood has changed drastically.

But at the same time, there’s still cause for concern. As good as the Patriots are playing – and entering their bye week, no one was playing better – this team is still walking the tight rope at several positions. And any more injuries could lead to big problems.

The Patriots return to action Sunday night, when they’ll take a 7-2 record and five-game winning streak to Indianapolis to play the Colts and the next big thing, Andrew Luck.

The Patriots have seemingly saved a season that appeared to be in trouble back on Sept. 29 when the Kansas City Chiefs buried them 41-14 on Monday Night Football.

That was the game that had Patriots fans running around crying, “The sky is falling, the sky is falling.”

And then Tom Brady reminded everyone how good he can be, Rob Gronkowski showed everyone how lethal he is when he’s healthy, Julian Edelman showed how shifty he is, and the defense showed how nasty it can be.

The Patriots were averaging 20 points (24th in the NFL) and 201 passing yards (30th among 32 teams) through four games. Brady was completing 59.1 percent of his passes, and his quarterback rating was 79.1.

Now, after putting up 201 points in their last five games, the Patriots are averaging 31.2 points (second) and 265.8 passing yards (eighth). Brady is completing 64.1 percent of his passes, and his rating is up to 103.5.

Brady says his faith in both himself and the team never faltered.

“I think you’ve just got to believe in what you’re doing, believe what you’re doing is the right thing, and if it doesn’t happen in the first three weeks of the season, you’ve just got to believe in it and keep working hard at it,” he said after the latest win, a 43-21 dismantling of Peyton Manning and the Denver Broncos – the team everyone thought was the best in the AFC.

“I think the guys really have believed in what Coach is talking about, and I think we’ve believed in one another and it’s gotten us to a good point.”

Now the hard part begins.

The Patriots are still the team to beat in the AFC East, maybe the entire AFC, and traditionally play better in the second half of the season. But they will be tested the rest of the way.

After Indianapolis, which has the NFL’s top-ranked offense and passing game, the Patriots host Detroit (with the league’s ninth-best passing game and top-ranked defense), then visit Green Bay (with quarterback Aaron Rodgers and receiver Jordy Nelson, among others) and San Diego (quarterback Philip Rivers and the 10th-best passing offense).

Then the Patriots come home to play the Miami Dolphins in a game that may decide who ends up as AFC East champion.

If the Patriots are going to come out of that stretch in good shape, there are three areas to watch:

n The offensive line: When the Patriots struggled early, the line was in shambles. Linemen were rotated in and out, and starters changed on a weekly basis. That led to confusion and sacks – 10 in the first four games.

Then the Patriots settled on a steady lineup: Nate Solder at left tackle, next to him veteran Dan Connolly, rookie Bryan Stork at center, veteran Ryan Wendell at right guard, and Sebastian Vollmer at right tackle.

The result? Only five sacks during the five-game winning streak. Brady has more time to throw and is finding more receivers.

Josh McDaniels, the Patriots’ offensive coordinator, said their chemistry has been a huge factor in the team’s surge.

“I think understanding how the guy beside you reacts to certain things, and the strengths and weaknesses of the guys that you’re playing with and the time spent working together, is something that can’t be understated,” he said.

But there are concerns. There isn’t a lot of depth on the line. Marcus Cannon is listed as the backup at three positions. Jordan Devey, Josh Kline and injured rookie Cameron Fleming are the other backups. All three struggled when they were in the lineup. An injury or two could set this group back. If that happens, the offense could struggle again.

n Running back: Stevan Ridley suffered a season-ending knee injury on Oct. 12, but he’s still the Patriots’ leading rusher. Ridley ran for 340 yards in six games – 30 more than Shane Vereen has in nine.

That’s all you need to know about the state of the Patriots’ running game. It is now in the hands of Vereen – a talented player in space but not necessarily from tackle-to-tackle – and Jonas Gray – who had three career carries coming into this season.

Rookie James White obviously isn’t ready. And Brandon Bolden has been relegated to special teams. So it’s up to Vereen and Gray to carry the running load.

No one expects them to lead the offense. That’s Brady’s job. But they need to be somewhat effective for the Patriots’ offense to run smoothly. Many of the passes rely on play-action fakes by Brady. If a team can’t run, the defense isn’t going to honor play-action fakes and the passing game will suffer.

Look for there to remain a concentrated effort to run the ball. And hope that no one else gets hurt.

n Linebacker: The Patriots were already thin at this position before Jerod Mayo was lost because of a knee injury on Oct. 12 – during the same game as Ridley’s injury.

Now they are relying an awful lot on second-year pro Jamie Collins, who is leading the team in tackles (59), and third-year pro Dont’a Hightower, who led the team in tackles last year (137).

After that? Yikes.

Akeem Ayers – acquired on Oct. 22 in a trade with Tennessee – is listed as a linebacker, but he’s more a replacement for defensive end Chandler Jones, who may or may not be back this season as he recovers from a hip injury. Ayers is a pass rusher who has already made an impact with sacks in each of his first two games for New England.

Chris White, a decent special teams player, and Jonathan Casillas, acquired in an Oct. 29 trade with Tampa Bay, are the backups. Casillas, a sixth-year pro, could be a factor as he gains more experience in the system. Deontae Skinner was given a shot but is now back on the practice squad.

So for now, Hightower, who has already missed two games because of an injury, and Collins, who has played exceptionally well the last two weeks, are going to take most of the defensive snaps.

How they hold up could determine how well this defense plays.

Coach Bill Belichick made it clear after the Denver game that the Patriots have a long way to go. Seven wins, he said, will get you nothing in the NFL.

For the Patriots to get to where they want to be – and that would be Phoenix in February for the Super Bowl – they need to keep moving forward.

They’ve done a pretty good job of that since a rocky September. Now let’s see if they can continue to do it.