The Mets made the moves Thursday night after a 6-1 loss to Atlanta.
Murphy had a MRI, and additional information was expected to be available on Friday.
''It's frustrating,'' Murphy said. ''It ended up being a little worse than I thought. It's frustrating to the other 24 guys in here. It's always nice to stay off the DL. I have to be smart about it and try to get healthy.''
The 20-year-old Herrera was called up from Double-A Binghamton. He was hitting a combined .319 with 12 home runs and 70 RBIs at Double-A and Single-A.