Country music star Carrie Underwood has said she is "so looking forward to seeing what God has in store" for her husband, Mike Fisher, after he announced he is retiring from the National Hockey League (NHL).

"Captain @mfisher1212 I sure am going to miss watching you play and cheering you on with the rest of Smashville, but I so look forward to seeing what God has in store for you in this next chapter of your life," the "Jesus Take the Wheel" singer wrote in an Instagram post. "You've given your teammates and the game your all for so many years...you've worked so hard and made us all so proud! Isaiah and I love you so much and are so excited to be able to have you home a lot more...We can't wait to cheer on the @predsnhl WITH you in the stands!"

The Nashville Predators captain, who played for 17 seasons, made the announcement in a penned letter published on The Tennessean, explaining that it was "the hardest decision" he ever had to make, but he knows it is the right one.

He wrote: "I kept praying for peace about the next step in my life. A peace that said this is God's will for your future. A peace that said whether or not this was the right time to walk away.

"I don't believe it came in a single instance or some aha moment, but as time passed, I gradually became certain that it was right for me to retire. I believe God gave me the ability to play hockey, and I was helped by dozens of individuals along the way, so it's not just up to me on when it's time to say goodbye.

"Knowing we were so close to winning it all in June only makes it more difficult to leave it behind, but I do so with hope. Endings are always tough, but I believe when something ends, there are new beginnings, new opportunities and new things to be excited for, too."

Fisher scored 18 goals and 24 assists last season, helping the Predators make it to the Western Conference title. Unfortunately, they failed to nab the Stanley Cup Final trophy after losing to the Pittsburgh Penguins in six games.

Both Fisher and Underwood, who have a son together, are outspoken about their Christian faith. In 2014, Fisher shared his conversion experience in a White Chair Film from I Am Second.

He recalled how, when he was 22, the Bible verse Luke 9: 23-25 changed his life. It reads: "If you want to be a follower of me, you have to put aside your own selfish desires, shoulder your cross daily and follow me. If you try to keep your life for yourself, you will lose it, but if you give up your life for me, you will find true life. What do you benefit if you gain the whole world, but lose your own soul in the process?"

"I remember that scripture just hitting me, that was for me," Fisher said. "I'd reached my dreams. I had money and everything. I thought I was cool and it just wasn't working. I knew where the answer was, but I hadn't been looking for it in the right places. Through a process of just praying and getting in the Word with my cousin my life was changed. For the first time, I remember thinking: 'Man, this is really real.'"

It didn't happen overnight, but slowly, God began to change his heart.

"I started to not worry about the dollars, but just focus on just pursuing him," Fisher shared. "And slowly, God started to just bring up stuff. I started to confess things in my life that I wasn't proud of. God just kind of released that. It wasn't religion anymore, it was a real relationship and it was awesome."