My boy needs serious help getting over his breakup?

So listen my best friend just got his heart broken by his girlfriend that he was with for over a year. He was in love with this girl and is havin some serious trouble with the fact that there over. He is trying as hard as he can to get her back but she dosnt want to talk to him anymore. She dosnt trust him because she thinks that he cheats. I cant say whether or not he did but she has no leads. He lied to her about where he was a couple of times but thats because he was trying to avoid a fight because he was in the same area of his X. He cannot focus anymore. In school hes zoning out and depressed. Hes a serious baseball player and now he can not even focus enough to hit the ball off the tee. can someone please help me figure out a way to get him out of this funk or maybe words for me to say to the GF. Im friends with her too. BTW he is not a partier at all i tried to make him go to a party tonight but he didnt want to go. also were only 17 almost 18. please help. thanks