Carlos Villanueva is quick to say he’ll have no complaints next season if he’s popping champagne in the clubhouse as a member of the Cubs bullpen. It would mean Villanueva had done his part paving the way for his rotation replacement Jake Arrieta. ‘‘I saw him pitch in Baltimore and here and he’s got great stuff’’ Villanueva said Friday in his first comments since losing his starting job. ‘‘If we can have a guy who can be a big contributor for next year in that role which I think he could be let’s see what it is.’’ Arrieta showed his best Friday in his second start for the Cubs shutting out the St.  Louis Cardinals on two hits through seven innings in a 7-0 victory. The Cubs scored more runs for Arrieta (1-0) in one game than they had for the rest of the staff in the previous six home games — and all he needed was one. ‘‘When anybody can throw a ball 90 mph spinning it that kind of thing and they have the velocity and have 97 mph in their back pocket when they need it it’s very intriguing’’ manager Dale Sveum said of Arrieta 27 who was acquired July 2 from the Baltimore Orioles in the Scott Feldman trade. ‘‘That’s the kind of stuff that the power arms can do — throwing strikes and making pitches. ‘‘We wanted to get him here with [pitching coach Chris] Bosio and see him and work with him and the system we have in place. We’re not judging anything just getting this guy to have command and understand how to use his pitches and do the things he can do with that kind of power arm.’’