Ever since free agency began on March 17, Houston Texans general manager Nick Caserio has been busy, busy, busy. Signing a record-number of free agents in the first 48 hours and executing four trades, Caserio made massive changes to their roster.

With new associate head coach and defensive coordinator in Lovie Smith, the Texans needed the defensive overhaul to make the transition to an effective 4-3 defense.

"Nick has done an excellent job," Smith said. "As you know, we were based out of a 3-4 front for quite a few years here, so there is a transition. The first thing, Coach (David) Culley, of course, Nick, we all got together to do was to start overhauling the roster to get our personnel to fit it. I feel like we're close to that right now. I love all of the free agency moves that we've made because some of the positions we're going to play with a little bit different guy."

In particular, Houston signed seven free agent linebackers after losing Tyrell Adams, Brennan Scarlett and trading Benardrick McKinney. In the past, the Texans did mix in 4-3 looks but Smith emphasized the need for a greater number of athletic and speedy linebackers in a 4-3 base scheme.

"Our linebackers are more space guys, run, speed as a premium with it. Having a four-man front now, we have to kind of adjust that a little bit, but I feel like we've done that. Our roster – we like our roster that we have right now before we add some more players in the Draft. Roster-wise, it's constant throughout. We'll always have that going, but we're making progress."

With three weeks remaining until the 2021 NFL Draft, the Texans will have a chance to add more talent to improve their defense that struggled against the run and forced just nine turnovers last year. Smith's defenses have been prolific at forcing takeaways in the past and he hopes to make that a daily part of his defensive philosophy in 2021.

"Explaining, defining, our defensive philosophy, there are some thing we want to get accomplished defensively," Smith said. "It all kind of starts with how you win football games – scoring points. I'd like for us to have a defense that realizes that, that the number one goal is to score. The second goal we have would be to take the ball away. We need to be good on third downs. In order to accomplish that, though, we want a smart defense that's fundamentally sound, that plays hard each down."

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