Fans and NFL players have been expressing their sorrow on Twitter following the unexpected death of Baltimore Ravens cornerback Tray Walker on Friday.

The 23-year-old player died from injuries sustained in a dirt bike crash in Florida on Thursday night.

The Miami-Dade Police Department said Walker's dirt bike collided with a sport utility vehicle at an intersection in Miami at around 7:50pm ET on Thursday.

Police said he was not wearing a helmet and was riding without lights at the time of the accident.

He suffered serious head injuries and underwent extensive surgery through Thursday night, however staff at Miami's Jackson Memorial Hospital were not able to save him.  Walker's agent, Ron Butler told NFL Media that Walker died at 5pm ET on Friday.

Ravens coach John Harbaugh paid tribute to Walker in a statement, describing him as a "young man with a good and kind heart".

"He was humble and loved everything about being part of the Ravens' team. He loved his teammates, the practice and the preparation, and that showed every day. He was coachable, did his most to improve and worked to become the best.

"I'll never forget that smile. He always seemed to be next to me during the national anthem; then we would give each other a big hug. May he rest in the Peace of Christ Jesus forever."

"God called u home ... God bless ya soul and it was a blessing to experience ya beautiful heart homie," his teammate Jeremy Butler tweeted.

Walker previously credited the faith of his late father to his being drafted.  He told the Baltimore Sun after the death of his father in November 2014 why he wanted to dedicate the season to his father: "This upcoming season, the whole process of right now, I dedicate that to him.  That's all he wanted. He just wanted the best for me and prayed to God that I would get this chance, and now I'm here."

Prior to Walker's death, Coach Harbaugh had sent this moving letter to his team urging prayer and pleading with them to make the right choices every day.

An Open Letter to Our Team

Men,

Right now, this moment is an incredibly difficult time for our Team and our Family. One of our Brothers, Tray Walker, is fighting for his life. I know we are showering him with, and covering he and his family, with Prayer and hope.

That was the kind of phone call you never want get as a coach, as a parent, as a brother, as a friend. This shook me and all of us. Like some of you, I haven't been able to rest since hearing the news late last night.

As I focused about Tray this morning, some thoughts came to mind that I wanted to share. What would I say to my own son, if I had a son, in a situation like this? You guys are that important to me.

This is what I would be saying to you in the team meeting room if we were together today: There is a lot going on out there and you are going to be involved in tough and difficult situations. You are making and will continue to make important choices pretty much every day. That's okay. That's our reality. It can even be very good to be put in different circumstances. To make it right, you are going to have to grow up fast. Probably faster than many of your friends and family.

Please remember to...

Lead in your home. Take care of Your Family and Yourself every single day. Think about who you are and where you are going, and what you stand for. Look after one another. Only then can you be your most effective on the job and in every area of your life.

Please consider your actions and choices. There are always consequences. Choose who you allow to advise you. Consider the quality of the council you take. Put yourself in positions to succeed. Turn away from unnecessary and risky behavior. Take care of your physical well-being. Live a healthy lifestyle. Pursue those things that make you better. Rest well. Eat well. Laugh with those who you love and love you. Fulfil your obligations effectively.

Be your own best friend. Do not be an enemy onto yourself. Turn away from trouble and harm. Walk away from foolish behavior. Ignore silly and unwise advice – You'll know it when you see it.

Get to know those people in your life who manage to walk free from the weight of self-created obstacles. Get close to those who have gone where you want to go, and have accomplished what you want to accomplish. Grow Spiritually. Think about what and who you want to become.

I am asking you to consider what is at stake in your life. Consider what your thoughts, actions and choices mean to those around you. Live your life fully and with purpose. Have fun and share your happiness. Find Your Faith, and allow God to Grow Your Faith.

Let's look out for one another. Be a great brother and friend. Inquire. Listen. Ask. Investigate. Reach out. Be There. Take a Step. Go For It.

Remember, We are Brothers in Arms. And, again, take care of each other.

John