Arbiter Harold Henderson is scheduled to hear testimony from NFL executive vice president for football operations Troy Vincent on Thursday, but he encouraged the NFL and the NFLPA to negotiate a settlement regarding Adrian Peterson's indefinite suspension.

A source told ESPN that there have been no offers exchanged yet.

"In our view, the league would have to show a level of reason and humility to present a settlement offer that would be acceptable," an NFLPA source said Wednesday morning. "Thus far, they have displayed neither."

Peterson will participate in Thursday's hearing via teleconference.

Henderson ordered Vincent to testify, over the objections of the NFL, after the union submitted an audio recording and transcript of a phone conversation between Vincent and Peterson.

Vincent allegedly told the Minnesota Vikings running back that his time on the commissioner's exempt list would be considered time served and that he would be suspended two additional games and not be subjected to the new personal conduct policy on domestic violence -- mandating a six-game suspension without pay -- if he attended a Nov. 14 disciplinary hearing with Roger Goodell.

Whether Vincent made the offer or had the authority to honor it remains unknown.

Peterson also declined to attend the November hearing with Goodell. At the time, USA Today Sports reported that Peterson told the league he would meet with Goodell to discuss potential discipline but would not attend the Nov. 14 hearing because there were too many unanswered questions about the process.

Four days later, on Nov. 18, the NFL suspended Peterson without pay for at least the remainder of the 2014 season for violating the league's personal conduct policy. He will not be eligible to apply for reinstatement until April 15.

Peterson immediately appealed the suspension.

The former NFL MVP hasn't played for the Vikings since Week 1 after he was charged with child abuse in Texas. He was placed on paid leave while the legal process played out, and he pleaded no contest Nov. 4 to misdemeanor reckless assault for injuring his 4-year-old son with a wooden switch.