MLB

DEALING CASTILLO WILL BE NO EASY TASK

LUIS Castillo is going to be very, very difficult to move this offseason. But maybe not impossible. The problem is the Mets would have to take on a headache to rid themselves of a headache.

To that end, The Post has learned that the Mets and Royals had discussions in July about swapping expensive malcontent outfielder Jose Guillen for Castillo. An executive who was aware of those talks said he thought it was possible the clubs could revisit negotiations this offseason.

Guillen is owed $24 million for the next two seasons; Castillo $18 million for the next three. So the Royals essentially would be adding $6 million of maneuverability for the next two years, save $6 million overall, but add $6 million to their 2011 budget. The Mets would have the reverse financially. Both players wore out their welcome last year after signing multiyear deals.

The Royals are losing second baseman Mark Grudzielanek to free agency and Castillo does offer one item they need, on-base skills. The erratic Guillen is hardly ideal, but he does have right-handed power to put in left field for the Mets. Again, this would be headache-for-headache, and one Mets official said he just as soon prefer to keep Castillo than take on the combustible Guillen.

In a similar scenario, the Diamondbacks considered shipping diminished righty-hitting outfielder Eric Byrnes (two years left at $22 million) for Castillo, but determined they just don’t like Castillo at all.

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The Yankees need a first baseman, and there is one out there with great similarities to where Tino Martinez was when the Yanks obtained his lefty swinging/superb defense combo after the 1995 season.

San Diego’s Adrian Gonzalez, despite playing in a pitching-haven home park, just produced a 36-homer, 119-RBI season during his age-26 season. In his final year for Seattle, Martinez went for 31 homers and 111 RBIs in his age-27 season. The Mariners, however, had financial concerns and dealt Martinez to the Yanks for Russ Davis and Sterling Hitchcock. Now the Padres are looking to reduce their payroll at a time when the Yanks badly need a Tino clone.

But Padres GM Kevin Towers put the chances of dealing his best offensive player from a team starved for offense at near zero.

“Adrian would be the most difficult guy for us to move,” Towers said. “I don’t see any circumstances in which we would do it. He is young, under control for three more years (at the incredible bargain total of $13.25 million), has plus offense and plus defense.”

Also throw in that Gonzalez is a San Diego native, which moved a rival executive to say, “If they traded him, I think even the laid back San Diego fans would revolt.”

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Towers, though, admits a willingness to deal ace Jake Peavy, who is very much on the market during this postseason. As of late week, the Mets had shown almost no inclination to pursue the right-hander. The Yanks seemed focused on trying to land their starting pitching via free agency and save their prospects for depth or to deal for other positions.

A few NL teams are hardest after Peavy with the Braves the apparent early front-runner. Several executives said the Padres were doing a lot of background work last week on outfielder Jordan Schaefer, a recent top Atlanta prospect whose reputation has taken a huge hit because of an early season HGH-related suspension.

The Braves have about $30 million to spend on their 2009 payroll and have targeted an ace. Peavy, a Mobile, Ala., native has a no-trade clause, but word is he would be amenable to Atlanta.

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Phillies left fielder Pat Burrell is a free agent and rival executives said Philadelphia is seriously considering a low-cost way to replace him: By moving third baseman/super pinch-hitter Greg Dobbs to the outfield. Dobbs hit .301 with nine homers in just 226 at-bats. He has played just 24 games in the outfield. But the rival executives said Phillies manager Charlie Manuel believes Dobbs can handle the outfield, especially remembering that he would be stepping in for the hardly fleet-footed Burrell, who is replaced late in games for defense by Eric Bruntlett.

Additionally, the savings in left would provide the Phillies the additional funds to pursue a No. 2 starter to work behind Cole Hamels and in front of Brett Myers.

Keep in mind, also, that the Phillies were peripherally part of July trade discussions for Manny Ramirez, and the free-agent slugger has a long association and great relationship with Manuel, his former hitting coach and manager in Cleveland.

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You want a surprise name that could end up out on the trade market? How about Dodgers catcher Russell Martin? Rival executives say the Dodgers are not overly enamored with his makeup and at a time when front-line catchers are hard to find, Los Angeles could decide to see what his value is. The Tigers, Marlins and Reds are all looking for catching, and the Red Sox would be, too, if free agent Jason Varitek departed.

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Daniel Murphy has continued to hit in the Arizona Fall League, which is no surprise. In his first six games, he was batting .429, and his on-base percentage was .522 as he had walked seven times against three strikeouts.

He is playing second base in the AFL, but not much should be read into that. Slots for the league become open around midseason, and at that time the Mets signed Murphy up to play second. To get a better idea where the Mets imagine Murphy playing in 2009, you should know the plan is to send him to Puerto Rico for Winter Ball and that he will play left field there. What is most interesting, however, is that the Mets scrapped the idea of playing him at first base this winter, though they privately concede there is a good chance that is where he will end up in the long run. That is a stronger sign that the Mets not only are going to pick up Carlos Delgado’s option, but that they also have no intention of picking it up and then trading him.

joel.sherman@nypost.com