WHAT IT MEANS: The Mets headed into the All-Star break on a down note.

Jon Niese surrendered four first-inning runs, then served up a three-run homer to Starlin Castro in the seventh, as the Cubs beat the Mets, 7-0, Sunday afternoon at Citi Field.

On-the-trading-block Ryan Dempster blanked the Mets for the first five innings in his return from the disabled list.

The Mets fell to 46-40 -- a still not-too-shabby record at the break. That’s five games behind the first-place Nationals, pending the outcome of Washington’s game against Colorado.

Chicago (33-52) won the season series from the Mets, 4-2.

The damage allowed by Niese was one run shy of matching his career high. He most recently surrendered three runs at Toronto in three innings on May 18.

Niese’s final line: 7 IP, 9 H, 7 R, 7 ER, 0 BB, 3 K.

GENERALLY SPEAKING: On the game telecast, Sandy Alderson offered little in the way of revelations while in the booth for an inning and a half. Alderson did suggest Zack Wheeler would make a couple of more starts at Double-A Binghamton, which the GM would like to see him “dominate." Wheeler then should move to Triple-A Buffalo. Alderson added, without mentioning lefty Josh Edgin by name, that the reliever likely would be promoted to the Mets from Buffalo shortly after the break (perhaps Jenrry Mejia, too) so team officials can gauge what they have before the trading deadline.

Alderson was not too explicit regarding trades. He did say he was conscious of the Mets' positive clubhouse chemistry and would try not to disrupt it. He also said, though, he would not stand pat just for the sake of chemistry and was hesitant to place too much importance on it. He added that an organization needs to be careful in acquiring a catcher in-season because of the unfamiliarity with the pitching staff, so it needs to be more than an "incremental" upgrade.

WHAT’S NEXT: David Wright, R.A. Dickey and Terry Collins head to the All-Star Game in Kansas City. NL manager Tony La Russa will announce on Monday whether Dickey will be given the starting assignment. (Wright finished the first half with a .351 average, three points shy of Jose Reyes' 2011 franchise record for an All-Star break.)

The Mets will regroup and hold a late-afternoon workout Thursday at Turner Field in Atlanta. Johan Santana (6-5, 3.24 ERA) takes the mound in Friday’s second-half opener opposite Braves right-hander Tim Hudson (7-4, 3.56).