For the last ten years, Jack and I have played for the same hockey team every Saturday. Jack is a better player than I am, but in the last few months he has had some trouble with his left knee, and he has found it hard to play a full game. He has seen the doctor several times about his knee, but the doctor doesn't know what is causing his pain. Jack has decided to take a break from hockey for a while, so that his knee can recover. It's going to be lonely on the team without him!
in this paragraph, the words "has decided" is : happened has a result now?
itīs the use of the present perfect for unspecified time in the past...
e.g . Yesterday Jack decided to take a break....or because itīs not important to say when he decided ,but the fact that he has decided it , we use the perfect tense.Got it?