But that decision didn't come without numerous interviews with the two-time Pro Bowl wide receiver and an extensive look into his background.
Speaking at his introductory news conference Thursday in Miami, Marshall said the trade in which the Dolphins surrendered two second-round picks to the Denver Broncos to obtain the wide receiver came after multiple phone conversations in which he convinced the team's brass that he would be more of an asset than a headache.
The Dolphins did their due diligence," Marshall said. "I think that's why I'm here. They got to really see what type of guy I am, and it worked out for the best."
Marshall said that type of guy is someone who plays with a great deal of passion and emotion.
"This game means a lot to me -- much more than just money," he said. "I play this game, not just to be another guy on the field, another guy in the NFL. I play this game to be one of the best, one of the greats. With that comes a lot of responsibility. Early on, I made my mistakes (and) worked through those things. I continue to look at myself in the mirror and continue to better myself."
Marshall said his past transgressions -- two domestic incidents with his then-girlfriend and numerous disputes with the Broncos' training staff and coach Josh McDaniels -- are all behind him. Marshall is looking forward to a clean slate in Miami, located just hours from Central Florida in Orlando, where he attended college.
"My past is exactly what it is -- the past," Marshall said. "I've made my mistakes, but me being 26 now, I may be young to some, but now I'm considered a veteran in this league. I think that with my experiences in the past, I can bring that into this locker room."
That should be music to the ears of Dolphins vice president of football operations Bill Parcells, who's known for taking on "diva" receivers.
"This may shock you guys, but I'm no prima donna," Marshall said with a laugh. "I like to get dirty. I'm going to get in there and mix it up a little bit. I just don't want to catch a lot of balls. I'll do whatever, hit the D-end, cracking back on linebackers. I think Mr. Parcells is the type of guy, if you bust your butt and do your job, you'll get a long just fine with him."
Likewise for Dolphins coach Tony Sparano, whom Marshall characterized as "my type of coach."
"I watch Coach on the sideline, get all red sometimes and just firey," Marshall said. "That's the type of coach guys like myself want to play for," he said. "At the end of the day, when it gets a little sticky (in) the fourth quarter, you'll be willing to run through a wall for those type of coaches. he expects a lot, he expects you to put team first. It's all about winning here."
"Here" is the AFC East, where Marshall's competition should be significantly stiffer on Sundays. Marshall likely will be lined up twice per season against the New York Jets' Darrelle Revis, who's widely considered the best cornerback in the AFC, if not the league.
"Where is Revis Island?" Marshall said, jokingly. "Hopefully I'll visit there soon."
"They're pretty good," Marshall said with a smile. "I've always thought that I was in a league of my own. My goal is to be No. 1. Am I that now? No. But with work and dedication, I'll get there. Hopefully it will be this year."