In his last four starts, Pineiro went 0-3 with a 14.85 ERA. He also gave up a total of 22 earned runs and 29 hits in 13 1/3 innings.
With his start on Wednesday acting as the final straw, Pineiro gave up seven runs on seven hits in just 4 1/3 innings.
"It is easy to see the results, and see he is pitching behind and the action on his pitches aren't as crisp," Scioscia said. "The real challenge is to find out why that is happening. Mike Butcher and Joel are trying to do that."
Understanding the challenge of going from a starting role to a bullpen role, Scioscia said the sinkerballer may have to throw some during and after games to get work in and stay fresh.
"You will take that step back and exhale, that's for sure. As far as getting the functional work in, it will be hit or miss," Scioscia said. "Bottom line, where J.P. is right now and where we need him to be, that divide was widening. We need him to take a step back and, hopefully, move forward with it."
Pineiro's move to the bullpen leaves an open spot in the Angels' rotation, however Scioscia wouldn't elaborate on who will take the position. A possible candidate could be reliever Hisanori Takahashi, who was a starter in Japan for 10 years and made 12 starts for the Mets last season.
With an off-day on Monday, Scioscia wouldn't need a fifth starter until Saturday against the Blue Jays. However, that may change, depending on Jered Weaver's appeal of his six-game suspension and whether he is available.
"We are going to need a fifth starter next week," Scioscia said. "There are a number of scenarios we will work through, and [they will] be contingent on where Weaver's suspension falls in."