Sports Illustrated has had a writer and photographer in town the last few days to do a potential cover story on the Cardinals’ rotation, which has had by far the best earned run average in the majors (2.38 before Friday) although one member of that rotation, veteran righthander Jake Westbrook, isn’t part of it now and may not be for a while. Westbrook, already on the 15-day disabled list with right elbow inflammation, said he is likely to miss another start beyond the two he was slated to be out because of continued discomfort in his elbow. He underwent an MRI and then took a second cortisone shot Thursday. Since Westbrook’s arm needed 48 hours to quiet down because of the shot, his scheduled bullpen session was scrapped Friday. Thus, he isn’t likely to come off the disabled list a week from Sunday, when he is permitted to. “The fact that I haven’t thrown yet means it would be tough to gather up enough arm strength to do that,” Westbrook said. “We did some more tests and discovered some scar tissue that wasn’t previously known about.” Westbrook, 35, also has been dealing with biceps tendinitis. He said the MRI showed that the previously inflamed elbow ligament and tendon were fine. The scar tissue was the new factor. “I think it’s just a combination of the amount that I’ve thrown over my career and the surgeries that I’ve had,” Westbrook said. “It’s definitely not a new elbow. There are a lot of things going on in there.