I wouldn't say it was haram, but I would say
1. If you watch a lot of sports i.e. more than around an hour a day, try to cut back drastically during this most holy of months, to pray, make du'a, read the Qur'an, do useful work, read meet worthy friends, help around the house etc.Maybe that's a lot for you, but just do what you can.
2. If the players are wearing shorts that show anything below the navel or above the knee, try not to watch, at least not on big screen so you don't notice insh!
May this be a truly blessed Ramadan for you, and all of us. (The Islamised version of Dickens' Tiny Tim, lol!)