Kansas City Chiefs running back Jamaal Charles has revealed that the 2014 season was the most frustrating of his career in the NFL.

The 28-year-old had his least productive season in the league since 2011, when he played just two games after tearing his ACL, as he struggled through a series of niggling injuries.

Charles has admitted that he forced himself to play through the pain barrier to help his team challenge for a place in the playoffs, but his attempts were in vain as they fell just short of the post-season.

"I was frustrated more last season as I've ever been because of all of those injuries," Charles told ESPN.

"I was frustrated because I didn't feel my body was right the whole season. But I battled through that time.

"That's all I could do. I felt like I was in a fight and I had to respond. I had 12 weeks to finish the season, and it felt to me like I had 12 rounds to go."

Charles recorded 1,324 yards from scrimmage and 14 touchdowns for the Chiefs in the 2014 season.