CHARLOTTE, N.C. -- It seemed like a no-brainer two months ago that the Carolina Panthers would activate Matt Kalil, their $55.5 million left tackle, as soon as he was eligible to return from injured reserve. The offensive line was a mess because of injuries.

Kalil was eligible to return on Monday.

There was no movement by the Panthers.

And according to coach Ron Rivera, there likely won't be with only a few days to prepare for Thursday's prime-time game in Pittsburgh (8:20 p.m. ET, Fox).

Even if this weren't a short week, it's unlikely the Panthers would have activated Kalil, the younger brother of starting center Ryan Kalil. That's how well his replacement, Chris Clark, and the rest of the offensive line have played during a 6-2 start.

Carolina has given up only seven sacks the past five games after giving up five the first two. On the season, they have given up the third-fewest quarterback pressures (55), trailing the New Orleans Saints (43) and Los Angeles Rams (53).

Two weeks ago, the line gave up zero sacks against Baltimore's top-rated defensive that had 11 a few weeks earlier.

"Our offensive line is playing as confident as they ever have," quarterback Cam Newton said. "For guys labeled as undesirables or misfits, they sure are doing a great job.

"C.C. with his leadership, being on a couple teams and playing with great quarterbacks, he understands what it takes to win."

In other words, the quarterback is happy, so don't upset the apple cart.

Replacing Clark with Matt Kalil might do that. Clark is second among Carolina offensive linemen, with a 63.1 grade, according to Pro Football Focus. Right tackle Taylor Moton leads the way at 78.9. Right guard Trai Turner is at 62.9, Ryan Kalil at 60.8 and left guard Greg Van Roten at 60.1.

But it starts with Clark, because he protects Newton's blind side.

"For him, knowing that at the left tackle position and helping guys like Sweat Pack [Moton], Trai and Rhino [Ryan Kalil] ... it's a correlation of guys putting great work in throughout the week and showing up on Sunday," Newton said.

It's one thing to throw a skill player back into the mix when healthy. It's another to replace a lineman when so much of what happens up front is based on chemistry, even though there never was a doubt last season that Ryan Kalil would return when he recovered from his neck injury.

But Ryan is a five-time Pro Bowler and team captain. Matt hasn't made the Pro Bowl since his rookie season (2012). Matt's last season with Minnesota, in 2016, was spent mostly on injured reserve with a hip injury.

Matt Kalil struggled the first half of last season with the Panthers. Despite improvement the second half of the year, his grade of 50.8 by Pro Football Focus paled in comparison to the 86.5 of then-right tackle Daryl Williams.

Kalil also struggled during the preseason, giving up two sacks against Miami before having his knee scoped and ultimately landing on injured reserve. So even when he returns, it could take a while to get comfortable.

Clark, 33, has been comfortable since signing the Tuesday before the second game after missing the second half of the 2017 season at Houston with an ankle injury. He played every snap that game and has a PFF above average grade of 63.1 since. He's doing it all with a one-year deal for the veteran minimum of $915,000.

So if Kalil were healthy enough to activate to the regular roster -- and he said weeks ago that he was on track to return on schedule -- how would you explain having your highest-paid offensive lineman riding the bench?

That alone could cause problems.

But Clark said it's not about that.

"Everybody is hungry," he said. "When you've gone through what we've gone through, getting to the Super Bowl and losing -- I did that at Denver -- you have that one goal, and that is to get back.

"Right now, we're getting it done. We're playing for our brother [Matt] and hope all goes well with that, but it's always next-man-up mentality."

As long as Kalil isn't active, there's no pressure to make a change. There is no deadline for the Panthers to activate Kalil, either. They will have 21 days to make the decision on what to do once Kalil starts practicing, and as of now, he hasn't done that.

You can't blame Newton if he wants to keep things the same. He's off to the best start of his career with 15 touchdown passes and 19 total touchdowns (including rushing) to only four interceptions. He had 19 touchdowns and 11 interceptions during his 2015 NFL MVP season.

Newton has been sacked only 12 times. The count was 20 this time a year ago.

You can't blame running back Christian McCaffrey if he wants to keep things the same. He's averaging 4.5 yards on runs between the tackles, compared to 3.3 a year ago.

It's a tricky situation for the Panthers and general manager Marty Hurney, who didn't negotiate the Kalil contract that has been criticized as too big from the outset. Former general manager Dave Gettleman is responsible for that.

Rivera has done his best to avoid the subject, saying he won't get into what-ifs about Kalil.

"We're in a good spot," he said. "It's one of those things that as [Clark] continues to play and Matt continues to rehab, we'll see how things go as we get down the line. But right now, we're in a good situation. We're very fortunate."

That makes maintaining the status quo a no-brainer.