When Kyrie Irving picked up his second foul 4 minutes, 29 seconds into Wednesday’s game against Brooklyn, things could have quickly unraveled for the Cavaliers. However, veteran point guard Jarrett Jack entered the game and took control. He had 12 points in the first half with Irving on the bench with two personal fouls. It illustrated one of the big reasons the Cavs signed the 30-year-old Jack to a four-year, $25.2 million deal in the offseason. Jack also pulled down three rebounds, dished out three assists and added a steal in his 23 minutes. The 6-foot-3, 200-pounder was 3 of 6 from the field, 1 of 1 from the 3-point line and 5 of 6 from the foul line. “That’s what I’ve hung my hat on for my entire career, and what I’m trying to bring to this team,” Jack said. “That’s one of the advantages you get from not starting. You can survey the game from the side. You try to be a spectator, to see what’s necessary on the floor during the course of the game and try to bring as much as you can.” The Cavs (1-0) had a good backup point guard in Shaun Livingston last season. Now they have perhaps the best backup point guard in the league. “He’s a veteran who has been through a lot of big games,” Cavs coach Mike Brown said. “There’s not much he has not seen. He doesn’t get easily rattled. “He’s great to come off the bench. He can change the pace with just his presence alone.” While talking to friends around the league, Brown said he couldn’t find anyone who said a bad word about Jack. “You see a guy who is tough,” Brown said. “You see a guy who is about the team. You see a guy who makes big plays and makes big shots. I’m happy he’s here.” Jack, in his ninth year in the league, admits he doesn’t get flustered in games. “I try to keep my temperature at an even keel, something I learned from Chauncey Billups and Jason Kidd,” he said.