This is the line drawn in the sand between Major League Baseball and its players union on the Pirates' disputed contract agreement with Pedro Alvarez:

When each side is heard Sept. 10 by arbitrator Shyam Das, the union will focus on the Pirates' dealing with their first-round draft pick and his agent, Scott Boras, maintaining that the team sought and received an extension to negotiate beyond the midnight Aug. 15 deadline and, within that, that the Pirates were granted a special favor. The union also will build a case that Alvarez's verbal acceptance of a $6 million signing bonus came after the deadline.

MLB will make the case that at least one more extension was granted, the one for the Kansas City Royals to negotiate with first baseman Eric Hosmer, their first-round pick and another Boras client. That way, MLB can argue that commissioner Bud Selig exercised his discretion in those cases, as he has with others, and that no special favor was granted to the Pirates.

In a clear attempt to buttress that argument, MLB, in an extraordinary move, ordered the Royals to take Hosmer out of action with their rookie-level affiliate in Idaho Falls, pending the resolution of the Sept. 10 arbitration hearing. That was disclosed yesterday, but Hosmer also was held out of Idaho Falls' game Thursday.

"Eric Hosmer will be held out until after the case is heard," MLB spokesman Pat Courtney said by phone from New York.

Kansas City was thrust into this scenario when Pirates president Frank Coonelly, in his statement Wednesday about the team placing Alvarez on the restricted list, mentioned that the Royals' agreement with Hosmer - also $6 million - was completed after the Pirates' agreement.

Royals general manager Dayton Moore yesterday acknowledged to Kansas City reporters having read Coonelly's statement but did not address which agreement might have been reached first.

"What I need to say is we agreed during the appropriate time frame and the terms were submitted in the appropriate time limit," Moore said. "That's all I can say about it."

Moore added that Hosmer is "very pleased" with his contract.

Hosmer does not lose any money for the moment, as teams are not obligated to pay signing bonuses until 90 days after the signing of a contract.

The Pirates and Boras declined to comment on the Alvarez matter yesterday, and that policy apparently will hold firm until after the case.

Here is a breakdown of each side appears to be building its case on the following issues:

According to a source on the MLB side, MLB's argument will be that the Royals' agreement was finalized after midnight, though it was not clear what position will be taken as to whether they or the Pirates came first. The Kansas City Star reported last night that Royals officials had the agreement done before midnight but were put on hold by the commissioner's office, which was dealing with the Pirates at the time.

According to a source on the union side, the union will not raise the timing of the Royals' agreement at all.

The union, in concentrating on the Pirates and Alvarez, will stress the minutiae of the events at the midnight deadline. That will include phone records showing a call from Boras' cell to the Pirates at 12:02 a.m., and it will be the union's contention that this was the call that resulted in Alvarez saying, "I accept," to validate his contract agreement.

The Pirates' stance has been that this critical call from Boras' office came at 11:58 p.m. and that "I accept" were among Alvarez's first words. But they have acknowledged that some aspects of completing the agreement formally with the commissioner's office came roughly a minute or two after the deadline.

Part of MLB's case will be that multiple calls were made in that span, and that the 11:58 call was the one in which Alvarez accepted.

The union's case could contend that the Pirates were granted a special favor because of the relationship between Coonelly and Rob Manfred, MLB's chief labor counsel. Before taking his current post, Coonelly served 10 years in the commissioner's office, much of it working closely with Manfred.

That is a charge, the source on the MLB side said, that the MLB is prepared to dispute vigorously.

The union will question why the Pirates did not seek permission from the union after the midnight deadline - on top of the permission granted by the commissioner's office - and will argue that such permission was necessary because baseball's labor pact of 2006 explicitly forbids agreements beyond midnight.

MLB will argue that the commissioner has latitude in such matters and, furthermore, that, because minor league contracts are involved, that the entire case should be excluded from the arbitration process.

What remains undetermined is what action the union will seek from Das. It is known that Boras would welcome reopening Alvarez's agreement in pursuit of a larger bonus, but such a ruling is without precedent.

MLB's preferred course of action will be simple: Toss out the grievance because it is "meritless," as Coonelly and Manfred phrased it Wednesday in independent releases. In the event of a ruling favorable to the union, MLB will seek to have judgment applied solely to future cases.