"Ask Tony Sparano how satisfied he has been with the Miami Dolphins' most recent class of newly arrived veterans —including linebacker Kevin Burnett, running back Reggie Bush and offensive tackle Marc Colombo — and Sparano will say he is indeed satisfied.

"I'm pleased with what they've done," Sparano said. "Every one of them is contributing right now and no question about it. When you're bringing in free agents like that, you want those guys to be out there and at the forefront. Those guys are."

Though Sparano says he's happy, nobody would fault him if he felt differently given the lackluster contributions of the newcomers. Amid the Dolphins' 0-4 start, the team's new additions have struggled to make a difference.

Here's a closer look at the Dolphins' three marquee acquisitions and how they've fared:

Kevin Burnett

The expectation: The Dolphins felt so strongly about Burnett that they released Channing Crowder, who had been one of the most vocal leaders on the Dolphins' defense. Burnett arrived from San Diego, where he'd excelled at inside linebacker in 2010, finishing with 95 tackles, six sacks and two interceptions. The hope was that he'd provide a significant upgrade over Crowder, both in terms of playmaking and the ability to defend the pass and cover tight ends.

The reality: Covering tight ends continues to be a weakness for the Dolphins, so Burnett hasn't helped there. Nor has he made any memorable plays — like his 29-yard interception return for a touchdown against the Colts a season ago. On paper, Burnett appeared to be an upgrade over Crowder, but he hasn't yet meshed into the defense. He has 13 tackles through four games.

Reggie Bush

The expectation: With the arrival of first-year offensive coordinator Brian Daboll came a new offensive philosophy for the Dolphins, who wanted to be more uptempo and pass-oriented. The Dolphins placed an emphasis on acquiring speed and playmaking ability and Bush, it seemed, fit both of those needs. Sparano spoke in the preseason with promise about utilizing Bush in a variety of ways in the passing game and allowing him a chance to become an every-down, featured back."