INDIANAPOLIS – There’s always a fine line between going about your business and adjusting how to go about your business when the unexpected occurs.

That adjustment is necessary for the Indianapolis Colts.

A rib injury sustained at Chicago will keep left tackle Anthony Castonzo out of Sunday’s game at Cleveland. It snaps his personal streak of 33 consecutive starts, including the playoffs, and ends the offensive line’s league-best streak of 22 straight starts as a unit.

More to the point, it re-introduces Le’Raven Clark into the starting lineup for the 13th time in his five-year career, but the first since week 5 of 2018. He started weeks 2-5 while Castonzo dealt with a hamstring injury.

 “I’m excited to see Le’Raven play,’’ Frank Reich said Friday on a Zoom conference call. “He came in here this year (and) I thought he had his best training camp. I really think he’s going to come in and play well.’’

He’d better.

Even with Castonzo, the Colts were bracing for what figures to be a difficult afternoon against the Browns’ defense. They feature end Myles Garrett, who has established himself as an early front-runner in Defensive Player of the Year discussions.

“This guy is one of the best players in the league,’’ Reich said earlier this week.

The 1st overall pick in the 2017 draft has an NFL-best 5 sacks to go along with six quarterback hits, three forced fumbles and two fumble recoveries.

Garrett generally lines up over the opposing right tackle, but the Browns move him around. They’ll undoubtedly station him over Clark until Clark and the Colts prove they can handle him.

“I’m sure (Garrett) will switch sides,’’ Reich said. “They’ll want to test out Le’Raven.’’

Pass protection is priority 1 every week, regardless the opponent. Through four games, that phase of the offense has been solid. Philip Rivers, who’ll never be mistaken for a mobile QB, has been sacked three times, and once was when he failed to gain any yardage on a scramble.

“We go into every week with a protection plan no matter who we’re playing and who’s playing for us,’’ Reich said. “It’s a comprehensive plan. We build into that plan adjustments we can make in-game.

“In one respect, it’s the same procedure that we always do. In another respect, ‘Okay, we know we’ve got a new starting left tackle.’ They’ll try to test that out and we’ll do the best we can do. We’re confident in our plan and we’re confident in Le’Raven.’’

Part of that plan includes offering Clark more help than if Castonzo was in the lineup. Look for a tight end to spend a good amount of time next to Clark, or a running back to chip at Garrett before going out of a route.

“It’s always a fine line,’’ Reich said. “The way we approach it is we stay balanced. We’re going to go a little bit of everything. We’ll give a little bit extra help. We’ll throw some rhythm passing game. You want to run the ball enough to keep them neutral.’’

A big part of that plan is for Clark to hold up his end.

The 2016 third-round pick has appeared in 39 career games, but his opportunities on offense have been scarce in large part because of the offensive line’s durability. Clark wasn’t on the field for any offensive snaps last season and had just 10 this year in mop-up time the last two weeks against the Bears and New York Jets.

Castonzo has been an offensive cornerstone since being selected in the first round of the 2011 draft. He’s started 144 of a possible 156 games overall, including 33 straight. It’s worth noting the Colts are 2-10 when he’s missed a game with an injury.

And for those interested, the left tackles who’ve stepped in when Castonzo has been sidelined: Clark (four games) and Joe Haeg (one) in 3028, Joe Reitz (three) in ’15 and Jeff Linkenbach (four) in ’11.

The Colts showed their appreciation for Castonzo in March when they signed him to a two-year, $33 million extension. He considered retirement before opting to return.

At the end of last season, Reich met with Castonzo and made his sentiments clear.

“Just made no bones about it: ‘we want you as our left tackle . . . there’s no one else we envision being our left tackle,’’’ Reich said at the time. “I think he had an unbelievable year (in 2019) and I think he’s the best left tackle in the league, I really do.

“I think the guys a stud player.’’

You can follow Mike Chappell on Twitter at @mchappell51.

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