KANSAS CITY, Mo. -- Tony Pena resigned as manager of the Kansas City Royals Monday night, less than two years after being named American League manager of the year.

Aaron Babcock, a Royals' spokesman, said Pena would be replaced on an interim basis by bench coach Bob Schaeffer.

The Royals lost a team-record 104 games last year, Pena's second full season in charge. After cutting payroll more than $10 million this year, the Royals are off to an 8-25 start, worst in the AL.

Pena has been subpoenaed to testify in a civil trial in the Kansas City area but has repeatedly refused to comment on the case, insisting it is a private matter.

Babcock said he "could not speculate" on whether Pena's unexpected decision was related to anything off the field.