Already facing the daunting challenge of becoming the NFL’s first repeat champion since 2004, the Broncos increased the degree of difficulty with quarterback chaos.

Peyton Manning retired, leaving a legacy worthy of Ring of Fame honors in Denver and a statue in Indianapolis. Brock Osweiler defected for Houston, taking $7 million more in guaranteed money there.

Osweiler’s exit from the Broncos created anxious moments, unexpected as it was. It also left me wondering: Could his departure be the worst and best thing to happen to the Denver offense this offseason?

Osweiler taking over represented a seamless transition, and based on the current quarterback depth chart, would have given the Broncos the best chance to win this season. In leaving, Osweiler created flexibility for the Broncos, leaving them with money to address glaring needs. They added offensive tackles Donald Stephenson and Russell Okung. Both bring questions but represent better potential fits in the zone-blocking system. Fixing the O-line was a priority and now creates several avenues to pursue in the April 28-30 draft. The Broncos kept running back C.J. Anderson. Had they re-signed Osweiler, they wouldn’t have matched Anderson’s four-year, $18 million offer sheet from the Miami Dolphins.

It can be argued fairly that the Broncos should have placed a second-round tender on Anderson, making him less appealing to other teams unwilling to surrender a draft pick. But if Anderson played for a $2.5 million salary and delivered, he would make more in free agency next year. As it stands, his contract is reasonable after this season if he stays healthy.

Osweiler leaves. Two tackles and a stronger commitment to a running back surface. Not a terrible trade-off.

Here is the other issue: I am not sure Osweiler is more than serviceable. While going 5-2 in seven starts last season, he flashed brilliance in victories over the Bears, Patriots and Bengals. He made throws that define elite quarterbacks. Then he didn’t. He held the ball too long, and his inexperience showed in lacking audibles. As the offense became more conservative, it no longer played to Osweiler’s strengths, leaving Manning as the best option to control the line of scrimmage and put the Broncos in the right running play.

Seven starts is not a long time, critics insist, to draw a conclusion about Osweiler. They are right. It’s not fair to assume he can’t do certain things based on a snapshot. But the contract he received from the Texans assumes he can, based on the same frame of reference. If he excels and leads the Texans to 11 victories — he must survive everyone’s predicted Thursday night season debut in Denver — then I am dead wrong.

Going back to my baseball parlance, it feels like Houston paid ace money for a fourth starter. Fourth starters are necessary and bring value through reliability. They become disappointing when the prism changes. For me, Osweiler at $18 million per season remains an uneasy proposition.

The Broncos wanted him back. Not panicking to re-sign him — assuming he would have taken their money — might benefit them. They addressed multiple concerns, and have myriad options at quarterback through a trade for Colin Kaepernick, signing another veteran or landing a top prospect in the draft.

The shock and Osweiler are wearing off. Defense defines this Denver team. The Broncos need a functional quarterback, not a star. If Mark Sanchez or the player behind door No. 2 can pull it off at half Osweiler’s price, Osweiler’s exit could define the offseason in a way never imagined when the Broncos’ anointed starter left for Houston.

Troy E. Renck: trenck@denverpost.com or @troyrenck