Rodney continues to throw the ball in the upper 90s, but has struggled much of the year after saving a Major League-leading 48 games last season while recording a 2.85 ERA.
"I really don't think it's fastball command," McClendon said. "I think Fernando was tipping some pitches and we've got to get that straightened out and get him to the point where he's not tipping anymore. Then I think you'll see him getting back to being productive again. When hitters know what's coming, it's a lot easier."
Rodney, 38, said he worked on some things in the bullpen on Sunday and will continue to iron out his delivery. He said opposing hitters seem to be lining up his fastball more than normal, but he's not sure why.
"The last three games I threw a lot of changeups for strikes and swing and misses," Rodney said. "It's different things, different approaches by Toronto, Detroit, the Yankees. When they face a pitcher they know, they try to find something.
"Some people say [I'm tipping]. Some people say they got the sign," he said. "I'll just keep trying and working. We'll get it figured out."
Rodney has been in the big leagues for 13 years, long enough to have gone through a lot of ups and downs as a reliever. He said his arm feels fine and his velocity has been strong, despite the results.
"I feel good," he said. "Maybe I feel a little location of the fastball, sometimes it stays in the middle. But I don't panic. If it's something I have to work out, I'm going to do it to get better. But I feel good. I'll just keep working."
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB, read his Mariners Musings blog, and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.