LaRon Landry has been with the Colts for the past two seasons and his impact has not been great. Landry was signed to a 4 year, 24 million dollar deal and has a 4.75M dollar cap hit this season. It will grow to 5.75M next season and to 7.75M after that. It's safe to say that he has not earned that money in his two years with the Colts, and saying he's even worth half that amount is pushing it. Landry has graded out negatively (-2.6), according to Pro Football Focus, this season and also graded out negatively (-4.7) last season. Landry has the ability to make plays, but did not show up in the two big games he played in this season (Broncos and Eagles) and had a few missed tackles on top of some missed assignments. He is not someone that can play in coverage; he is constantly beat when matched up against tight ends or even when he's in zone based coverages, and he has trouble taking on the receiver in his zone. Last season, quarterbacks throwing his way had a 115.3 passer rating. This season, it's an 86.7, but Peyton Manning had a perfect 158.3 rating against him and games against Chad Henne and Charlie Whitehurst will only deflate that passer rating. Both of those stats indicate his poor play in coverage.
His four game suspension for performance enhancing substances should only make the Colts organization more angry with him.
Sergio Brown has played in the place of LaRon Landry. Brown has graded out positively according to Pro Football Focus in the 4 games he has started and on top of that, he has a sack, 12 tackles and quarterbacks have a 62.7 quarterback rating when throwing his way. He has proven to be solid in coverage, but brings a different element as he can blitz the quarterback very well and the Colts blitz him a few times each game. They do not have that element with LaRon Landry. As mentioned before, Brown is the guy replacing Landry and he is simply outperforming him on the stat-sheet and on the game film. You always should stick with the hot hand and Brown is the hot hand. Landry before his suspension was not hot.
MIke Adams has played in a different role from Brown, but has played it extremely well thus far. Pro Football Focus rates him as the fourth best safety in the NFL this season (with a grade of +8.6). Adams has 34 tackles on top of 2 interceptions and 3 pass deflections. He has plenty of experience and seems to thrive in this system. He's a lock as the starter for at least the next several games, if not the rest of the season.
The Colts defense has taken a big step up without Landry in the lineup. In the four games without Landry, the defense has allowed, on average, 21 points (opponent point total not counting the Luck Pick Six in the Steelers game). They've won three of the four games, all three against teams who when they played against the Colts, had winning records. They allowed a total of 41 points in the three wins and shutout against a good offense in Cincinnati.
Although LaRon Landry has the experience, it's safe to say that the Colts are performing better as a defense with Brown and Adams. That is all that matters. Some could argue that the defense isn't great after a terrible game against the Steelers, but I'll hold the three wins before the Steelers as a better sample for telling how good this defense is.
LaRon Landry has not done anything to deserve getting his job back. His play has been anything but consistent and he's been a liability in coverage and for a guy who many know as a hard tackler, has several missed tackles in the last two seasons. Sergio Brown brings more consistent, is a better all around player and is the safer bet going forward.