Few baseball analysts outside Chicago know the Cubs better than Dan Plesac. Plesac's history as a Cub left-hander and Chicago-area native made him a natural candidate last fall for the WGN-Ch. 9 analyst job that eventually went to Jim Deshaies. Plesac signed a contract extension to stay at MLB Network, where the colorful commentator begins his daily spring-training look at “30 Clubs in 30 Days” on “MLB Tonight’’ at 5 p.m. Friday. Before Plesac started his tour this week, the former CSN Chicago studio host answered several questions about the Cubs. Q: Which new Cubs veteran starting pitcher acquired in the off-season will make the most impact? A: Edwin Jackson. He’s had a bad knock on him. He’s one of those guys who falls into the category: Is he a top of the end rotation guy on a good team? He stays off the disabled list, gives you innings, takes the ball and pitches with a lot of guts. For what the Cubs are looking for, he’s a real good fit. He’ll give you innings and some leadership and a guy like Jeff Samardzija can watch him. Q: Speaking of Samardzija, can he be the ace on a Cubs staff that contends for a division title when they finally are ready to contend? A: Absolutely. The hardest thing to do with pitchers is to have patience. Forget about his first couple seasons. He was kind of a victim of his own circumstances. His arm was so good, that the easy thing to do was call him up, put him in the bullpen, throw a couple pitches and it worked. But I think long-term he’s better suited to be a starter. His other pitches are starting to develop. He took a lot of steps forward last year but sometimes it takes a pitcher, two, three, four seasons and this is really only his second full season in the rotation as a starter. If you see as much progress in 2012 as you saw in 2012, I’d say no question he’s a guy who’s going to be around when this thing gets turned around. Q: Is the faith in Carlos Marmol as the closer justified? A: It boils down to one thing, the command of his pitches. I’ve always thought he had better command of his slider than his fastball. He gets in slider-happy mode because he can throw it for strikes. The games that Marmol pitches bad, very rarely it’s the team that beats him. He beats himself. He falls behind in the count. If he can put the things off the field aside, and throw strikes, he’s as nasty as any right-hander and can be a dynamite closer.