Cockcroft: Welcome Baaaaack ...

Somehow, when I think about much of the baseball news that broke Monday afternoon, the "Welcome Back Kotter" theme song can't help but creep into my mind.

It was an afternoon of players re-signing with their 2007 teams, guys whose fantasy values, at least on the surface, probably won't significantly change. Still, interesting story lines surround each, so let's take a quick look at the implications:

Yankees welcome back Mariano Rivera

Rivera told the Yankees on Monday that he's accepting their three-year, $45 million contract offer, pending a physical, according to ESPN.com's Buster Olney. That presumably keeps Rivera, No. 3 on the all-time saves list (443), in pinstripes through the end of his career.

As closers go, you can't get much safer than Rivera, who has averaged 40 saves per year and -- with the exception of disabled-list stints -- has never lost his job since taking over for John Wetteland following the 1996 season. He's consistent, durable and pitches for one of the most successful teams in baseball, all things that virtually guarantee him a spot among fantasy's top 10 closers at season's end, even in 2008.

Still, Rivera's 2007 statistics showed subtle signs of a decline, and with him set to turn 38 on Nov. 29, we might be about to witness the career decline of one of the greatest closers in baseball history. Accounting only for his 12 seasons as a full-time reliever -- in other words, since 1996 -- Rivera set career worsts in 2007 in ERA (3.15), batting average allowed (.248), OPS allowed (.645) and pitches per inning (15.8). His WHIP (1.12) was also his worst since his first year as a closer in 1997 (1.19), and he earned a save in only 45 percent of his appearances, his lowest rate since taking over as Yankees closer.

Sure, there's probably another year or two of top-10 closer production left in Rivera's right arm, but that third year might be a doozy. Expect similar numbers in 2008 to his 2007, or perhaps slightly worse, and don't be shocked if he's only an above-average closer in 2009, the year new Yankee Stadium is scheduled to open.

Red Sox welcome back Mike Lowell

Olney also reported Monday that Lowell agreed to a three-year, $37.5 million contract to remain with the Red Sox, but only after the third baseman declined a four-year, $50 million offer from the Philadelphia Phillies. Strangely, had Lowell actually departed Boston, Philadelphia was one destination fantasy owners might not have minded.

Part of the reason Lowell's owners -- or prospective 2008 owners -- won't be so concerned now that he's back with the Sox are his 2007 home/road splits. He was a .373 hitter with a .418 on-base percentage and .575 slugging percentage in 77 games at Fenway Park, but only .276/.339/.428 in 77 road contests. The latter would amount to only a .280-15-90 type batsman, which would actually rank as average to slightly below for fantasy.

Of course, it could be argued that much of the motivation for Lowell's 2007 bounce-back season was his playing for a new contract. Now enjoying contract security through 2010, Lowell seems more likely to finish with 2008 numbers closer to 2006's .284-20-80 line. Still, that's not bad for a third baseman, and it might represent his minimum expectation, as an everyday No. 5/6 hitter in such a potent lineup.

Mets welcome back Luis Castillo

He might not be an exciting name for fantasy, and it's possible the Mets might regret the deal before its conclusion, but Castillo's four-year, $25 million contract agreed to on Monday shouldn't be taken too lightly. A midseason acquisition in 2007, Castillo provides the Mets with perhaps their most effective No. 2 hitter in more than a half-decade.

Castillo batted .296 with 10 stolen bases and 37 runs scored in 50 games for the Mets after coming over from the Minnesota Twins; scaled to a full season, that's 28 steals, 105 runs. Hitting between Jose Reyes and David Wright, Castillo could be good for another 100-plus run season, and while his speed is in decline, he's capable of as many as 20 steals. A .294 career hitter with a .368 on-base percentage, Castillo rarely gets the credit he deserves in fantasy, and he's in perhaps the best situation he has ever been in his 12-year career. He might suffer a steep decline by the final year of his new deal, and he might not finish with much better than his 2007 numbers, but he should finish in the ballpark of that, too.

As for the remainder of the Mets' lineup, here's an interesting stat to consider: In Castillo's 49 starts in the No. 2 hole in New York, the team averaged 5.51 runs per contest. In the Mets' other 113 contests, that number was 4.73. Small sample size, sure, but it helps demonstrate how much deeper the Mets' offense is with Castillo helping set the table. That might mean as many as 10 extra RBI chances for Wright and Carlos Beltran.

Tristan H. Cockcroft covers fantasy sports for ESPN.com. You can e-mail him here.