The Indianapolis Colts have experienced quite the transformation in a little under two years.

Andrew Luck's healthy return in 2018 resulted in a 10-6 record and a Wild Card win. The offensive line had been revamped, resulting in a Pro Bowl season from Luck and a balanced running game. But things were about to change rather significantly.

Luck abruptly announced his retirement in August 2019. Jacoby Brissett went 7-8 in what essentially amounted to an emergency starting role, but the Colts missed the playoffs.

General manager Chris Ballard subsequently went to work in the offseason. He signed veteran quarterback Philip Rivers and made a blockbuster trade for DeForest Buckner, giving the Colts impact players at positions of need.

Indy went 11-5, but came up short in a Wild Card loss to the Buffalo Bills. Rivers has since retired, and Ballard faces an offseason that will likely demand some revamping of the secondary and finding a new left tackle to replace left tackle Anthony Castonzo, who retired earlier this month. All this on top of finding a new quarterback.

Much of the focus is sure to be on the Colts' quarterback search. But Indy also has the second-most projected cap space, per Over The Cap. Ballard will have the opportunity to plug holes as the Colts hope to join the elite tier in the AFC.

Here are three free agents the Colts could target this spring.

3. Allen Robinson

It remains to be seen whether the Colts will re-sign franchise staple T.Y. Hilton. Team owner Jim Irsay said he would love to bring Hilton back into the fold, but noted there are no guarantees:

Hilton has meant quite a bit to the Colts over the years. He developed a strong rapport with Luck, in particular, going over the 1,000-yard receiving mark in five of six years between 2013 and 2018. But injuries and age have made him slightly less explosive.

If Allen Robinson's market isn't absolutely insane — which it very well might be — the Colts should at least see what it would take to sign him.

Robinson is coming off consecutive 1,000-yard seasons with the Chicago Bears, in spite of underwhelming quarterback play and pass-catching depth. He had 151 targets and 102 receptions, with just three drops. He is one of the more sure-handed receivers in football, capable of making spectacular individual catches and winning one-on-one matchups.

The Colts have some talent in the receiving corps. Zach Pascal (a restricted free agent) and Michael Pittman Jr. both offer playmaking. Parris Campbell has plenty of talent, but he has not been able to stay healthy.

However, Indy lacks a true No. 1 wideout. Maybe re-signing Hilton is the answer. However, Robinson is nearly four full years younger and has produced throughout his career despite playing with some unsavory quarterbacks. Imagine what he could do in Indianapolis were the Colts to, say, trade for Matthew Stafford.

Robinson might well be too expensive. Still, the Colts should make overtures, at the very least. Kenny Golladay and Chris Godwin might also be interesting options if Ballard chooses to go a different route at wide receiver.

2. Alejandro Villanueva

It seems like a pretty good bet Ballard will place a premium on finding a new left tackle, whether via free agency of the draft.

The Colts GM recently said he believes games are won and lost in the trenches, which in part explains why he was willing to give up the No. 13 pick in the 2020 draft so as to acquire Buckner:

“I believe in my soul that's where you win,” Ballard said, via Jim Ayello of The Indianapolis Star. “You win up front in this league.”

So, how will the Colts address the blind side?

Indy could elect to move All-Pro left guard Quenton Nelson to that spot. But it seems more likely the Colts make external upgrades.

Now, the draft could very well be the best option for addressing the position. The 2021 class is fairly stacked at left tackle, which is good news for the Colts. Indy is already paying Ryan Kelly quite a bit of money, with extensions for Nelson and Braden Smith almost sure to follow. Thus, drafting a left tackle could keep costs down (relatively speaking) and add more young talent.

Of course, there is a good chance the team's first-round pick (No. 21) is dealt in the event Ballard trades for a quarterback like Stafford. Adding through free agency has to be a consideration, at the very least

Pittsburgh Steelers left tackle Alejandro Villanueva is a strong option. Villanueva made the Pro Bowl in 2017 and 2018, and has played all 16 games in six consecutive seasons.

Yes, Villanueva is 33, and there is never any guarantee aging offensive tackles will stay healthy. But he is likely to be less expensive than both Trent Williams and Russell Okung, and is still a very capable player at the position.

The Colts might also pursue a younger right tackle (perhaps Buffalo's Daryl Williams) and move them to left tackle. But Villanueva is a decent option.

1. Yannick Ngakoue

The Colts have a pair of defensive ends hitting the open market in Justin Houston and Denico Autry. This affords Ballard to keep his options open when it comes to addressing the trenches on the defensive end.

One of Houston or Autry could return next year. Re-signing both seems unlikely, especially if Ballard feels there is an upgrade out there on the open market. Yannick Ngakoue certainly could be an upgrade.

Ngakoue has not quite been the same world-beater he was with the Jacksonville Jaguars in 2017 and 2018. But the Washington, D.C. native has yet to turn 26 years old and is still producing at a high level.

Ngakoue had 8.0 sacks and four forced fumbles in each of the last two seasons. He still put up numbers upon being traded to the Baltimore Ravens, despite having a bit of an inconsistent snap count as part of a loaded defensive line.

The Colts could very well go after Ngakoue, who might be a better fit in Matt Eberflus' 4-3 scheme. Indy would have a lot of speed with Ngakoue and Buckner on the same line, which could be a nightmare for opposing quarterbacks.

What about the cornerback position?

Patrick Peterson

Peterson's All-Pro days are in the rearview mirror at this point. But Xavier Rhodes revitalized his career in Indy in 2020, and Peterson might experience something similar.

Brian Poole

Poole had two interceptions and seven passes defended in nine games with the Jets. The 28-year-old has a strong frame and could excel as a press corner.

Michael Davis

Davis only just turned 26 and is coming off a season in which he had three interceptions and 14 passes defended. Opposing quarterbacks had a 60.6 percent completion rate when targeting Davis.