Anderson has taken 13 Championship wickets to date
James Anderson has said his time as England's 12th man at the ICC World Twenty20 set him back after a good start to the season.
Before going to the West Indies, the 27-year-old pace bowler took nine wickets in Lancashire's County Championship win against Essex.
He told BBC Radio Manchester: "Having not played the past few weeks, I felt like it's put me back a little.
"I thought I was making good progress before I went away."
Anderson added: "It was very frustrating in the West Indies. I had come back from the injury and felt fit and strong. I was looking forward to playing some cricket when I went out there but it didn't work out like that.
"I just felt that rustiness again that I had at the start of the season.
"Obviously, it is a squad effort and I was there in case someone got injured.
"I had to do jobs like running drinks out. Although the management would say I was part of things because I was helping off the field and bowled at the guys in the nets, it's not the same as playing."