The Cubs are waiting for more information on C.J. Edwards, their top pitching prospect who’s said to be feeling some tightness in his right shoulder. Edwards traveled to Chicago on Thursday and was examined by Dr. Stephen Gryzlo, with an MRI scheduled for Friday morning. The Cubs will have a better read on the shoulder issue at that point. As a precaution, Edwards had to shut down his last side session with Double-A Tennessee, where he’s gone 1-0 with a 2.61 ERA in four starts, showing the stuff that made him the centerpiece in last summer’s Matt Garza trade with the Texas Rangers. A 48th-round pick in the 2011 draft, Edwards has emerged as Baseball America’s No. 28 overall prospect. His skinny frame – he’s listed at 6-foot-2, 155 pounds in the media guide – has led to questions about his durability. He has also put up 260 strikeouts in 204 career innings in the minors. The Cubs understand they will need good health and a certain amount of luck as they rebuild through the farm system.