Kiko Alonso is living proof that fortunes can change rapidly in the NFL.

Just one year ago, the Miami Dolphins weren't exactly sure what they were getting when they acquired Alonso and corner Byron Maxwell in a trade with the Philadelphia Eagles. Alonso was coming off multiple knee injuries and didn't look like the same agile, athletic linebacker he was during his rookie season with the Buffalo Bills.

Alonso was pretty much a throw-in, because Miami needed cornerback help and wanted Maxwell. Alonso had one year left on his contract in a "prove it" season before becoming a restricted free agent. He had shown enough potential in Buffalo that Miami figured it was worth a shot to see what Alonso could do at this stage of his career if he got healthy again.

Alonso led Miami with 115 tackles, and on Tuesday he signed a four-year extension that keeps him under contract with Miami through the 2020 season. It's the type of rapid turnaround that doesn't happen often with the Dolphins, and Alonso said he is happy he is staying in South Florida long-term.

"It means everything," Alonso said on a conference call with the Miami media. "This is where I want to be. I'm just excited that it's official that I'm staying here.

"I love my coaches. I love my teammates. I know we're building something special here and I want to be a part of it."

Alonso quieted critics by consistently finishing plays, staying around the football and helping Miami win 10 games and reach the playoffs for the first time since 2008. His best play was a game-closing pick-six for 60 yards in a win over the San Diego Chargers.

But perhaps the biggest key was Alonso's health. For the first time in a while, he had no knee issues or durability questions. The Dolphins hope that trend continues, although Alonso did play through a hamstring injury and a broken thumb that was surgically repaired this offseason. He only missed one game.

Alonso, who is listed at 239 pounds, is on the smaller side for NFL linebackers, and he also plays with reckless abandon. Those two factors have the potential to lead to injuries.

"That's just the way I play," Alonso said. "I've played like that since high school and since I played in the backyard with my friends. Health-wise, I'm not going to change the way I play. So it is what it is."

The Dolphins expect to move Alonso to outside linebacker, where he doesn't take the same physical pounding and can better preserve his health. The stakes now are higher for the Dolphins, considering last year Alonso was a one-year rental, but this season he is a four-year commitment.