Back near the time of the 2016 NFL Draft, Sports Illustrated ran a story telling the extensive oral history of the 2011 Draft. The story didn't really receive as much attention at the time as it was overshadowed by this year's draft (understandably so), but the story did contain an interesting tidbit about the Colts.
NFL Films senior producer and analyst Greg Cosell was one of those interviewed for the story, and he said that the Colts were deciding between tackle Anthony Castonzo and quarterback Andy Dalton in 2011. Here's what Cosell said:
Castonzo was taken in the first round by Indianapolis [at 22]. But I know for a fact they were debating between Dalton and Castonzo. That was back when they had the QB question, with Peyton’s neck [injury].
We've heard plenty about Dalton in connection with the Colts in recent years, particularly with former Colts general manager Bill Polian saying that if he had taken Dalton in 2011, he'd still be Indy's GM. We know that in hindsight Polian wishes he would have taken Dalton, but this report is as definitive as we've gotten about the Colts' actual interest in the quarterback during the draft. Greg Cosell makes it sound like the Colts really were considering drafting Dalton and were torn between him and Castonzo.
Obviously, Castonzo has done quite well for himself in Indianapolis, as he has started 73 of 80 possible games for the Colts since being drafted. He has established himself as one of the better left tackles in football and the blindside protector for Andrew Luck. But the reality is that Castonzo never played a single snap protecting Peyton Manning, as the franchise quarterback missed the entire 2011 season due to a neck injury before then being cut to make way for Luck.
If the Colts had drafted Andy Dalton, it would have had a major impact on the Colts and on the NFL. The Colts likely would have won more than two games in 2011 (though perhaps not too many more) and therefore would have kept Peyton Manning. The quarterback likely would have finished his career in Indianapolis, but when considering the talent-level it's very possible he wouldn't have enjoyed the same success that he did in Denver. Dalton, meanwhile, would have sat the bench behind Manning. The Broncos wouldn't have gotten Manning and therefore wouldn't have had a record-breaking offense, and another team - like the Jaguars - would have gotten Andrew Luck.
So while drafting Andy Dalton really might have saved Bill Polian's job in Indianapolis, it worked out better for the franchise as a whole that the Colts drafted Anthony Castonzo in 2011 - as that may have directly or indirectly led to the drafting of Andrew Luck, which has set the Colts up for another decade of success. And to top it all off, he'll have a solid left tackle protecting his blindside for the foreseeable future, too.