Let's start with a big assumption - Ty Sambrailo will be our starting left tackle - and move from there. We can debate the chances of this occurring in the comments.
Maddeningly Hard to Sack
Peyton Manning is the master of avoiding sacks. He does this by throwing the ball before the defense can get to him, not by slipping out of the pocket like many NFL quarterbacks. Here are his team's rankings in terms of sacked percentage (sacks allowed/total drop backs)
So the worst a PFM-led offense has fared was in 2001 with a veteran LT. In 2001, the Colts had veteran first-round pick Tarik Glenn starting all 16 games. Despite that, Manning had his worst year in terms of getting sacked (29 times, 5.5 percent of all drop backs).
Let that sink in. In his WORST year, Manning was sacked 29 times (1.8 times per game). The Lions allowed a league worst 66 sacks that year. Manning was close to the bottom of the league in INTs that year with 23 (26 was the worst). Other than his rookie year, 2001 was his worst year in the league statistically with 26 TDs and 23 INTs. Something was "off" with the Colts offense and Peyton in 2001. It's possible that this was a result of his offensive line that year.
So how did he (and the Colts) fare in 2007 with a rookie second-round draft pick, Tony Ugoh, starting 11 games at left tackle? He ONLY threw 31 TDs (tied for fifth that year) and 14 INTs (tied for 10th), completing 65.4 percent of his passes en route to a 13-3 record. He was sacked a grand total of 21 times in 2007 (4.2 percent of drop backs).
Ugoh started the first six games, and the Colts were 6-0 at that point. He got injured and Charlie Johnson started the next five games during which the Colts went 3-2. Ugoh returned for the final five regular season games, and the Colts finished the year 4-1 in those games - with the only loss coming in the "mail-it-in" game in week 17 that didn't matter to the Colts (Jim Sorgi played most of the game in place of Manning). So in essence, the Colts went 10-0 with a rookie second-round pick starting at LT.
Running game assist?
So maybe Ugoh and Manning were helped by a strong running game, which could take pressure off a rookie left tackle, right? Nope. The Colts were 25th that year in yards per carry (although they did score 19 rushing TDs, three by Manning). Despite the threat of the pass, light boxes and a lot of carries, Joseph Addai was only able to muster 1,072 yards on 261 carries (4.1 yards per carry) with a long of 23 yards. That 23-yard carry was the longest carry for the Colts that season. So, despite many advantages, the Colts running game in 2007 was poor.
While Manning is older, the Broncos' 2015 running game should be significantly better than the 2007 Colts running game. C.J. Anderson is a much more dynamic/explosive running back than Addai ever was. We also have the high expectations coming from the return of Gary Kubiak and the ZBS. Our running game is expected to be good, if not elite.
Why does this matter to us? I expect to have a rookie starting at left tackle (unless Sambrailo really stinks it up in training camp). At this point we could still have an offensive line with veterans starting at every position, but here's my speculative OL with what we know right now:
LT - Ty Sambrailo
LG - Ben Garland
C - Gino Gradkowski
RG -Luis Vasquez
RT - Ryan Harris/Chris Clark/Michael Schofield
There should be a lot of parallels between the starting offensive line of the 2007 Colts and my tentative starting line for the Broncos.. The Colts had one All-Pro and perennial Pro-Bowler in Jeff Saturday at center. We have one All-Pro and perennial Pro-Bowler in Vasquez. The Colts had two undrafted players starting (Ryan Lilja and Saturday). If Clark and Garland start, we will be starting two undrafted players on the OL as well.
Despite that, the Colts still went 13-3 and were able to lock up the second seed in the playoffs. Unfortunately for them, the Colts lost at home to the Chargers in the divisional round. That appears to be the fear of many in Broncos Country - not that we will suck this year, but that our offensive line will hold us back enough to keep us from the ultimate prize once again. The offensive line was a contributing factor in the early playoff exit of the 2007 Colts.
Another parallel to the 2007 Colts is the defense. The 2007 Colts had a very good defense - leading the league in points allowed (16.4/game) and coming in third in yards allowed. They also forced the second most turnovers. The 2007 Colts ran a 4-3 with Robert Mathis and Dwight Freeney in the their primes. They also featured a pair of very good safeties in Bob Sanders (two time All-Pro and NFL Defensive Player Of the Year in 2007) and Antoine Bethea (three-time Pro-Bowler).
In spite of that, they still failed in the divisional round like we did in 2012 and 2014. Their defense was unable to stop Billy Volek from leading the Chargers on the game-winning touchdown drive in the 4th quarter - that's a fairly epic choke by a defense right there. I will note that Manning had two drives to try and regain the lead, the first of which ended with an incomplete pass to Addai on 4th and goal from the 7 (down 4 with two minutes to play).
I, along with most of the staff, expect our defense to be very good, possibly elite this year. There will be an article soon detailing why we think the Wade Phillips 3-4 with our talented defensive roster is going to be elite in 2015.