Robb Nen's injury problems could put the NL West up for grabs. Brad Mangin/SI

By the time spring training officially wraps up Sunday, millions of practice grounders, thousands of hours of batting practice, hundreds and hundreds of mind-numbing infield drills and close to 500 mostly meaningless games -- featuring such powerhouses as the Yankee Future Stars, Florida Atlantic University, Manatee Community College, the Sacramento River Cats, the Midland Rockhounds and, yes, the Detroit Tigers -- will have been committed.

From Tokyo to Tampa, from Surprise to Fort Myers, from Las Vegas to Lee County, baseball -- by the time this is over -- will have spent the past six-plus weeks shaking the rust off and breaking down the results.

So, what do we learn from spring training?

Well, here are a few undeniables ...

You better believe the Cubs are worried about Mark Prior.

And they should be, too. Their ace is out until at least early May because of a cranky Achilles tendon. And now comes word that his throwing shoulder is a little sore, too. Missing all of April probably would cost Prior at least five starts. Last season, he went 4-1 in April. In a tight division like the NL Central, that could be critical. Maybe Prior's replacement makes up for his absence. Maybe not. It's certainly enough to give Cubs fans ulcers -- especially considering that Kerry Wood already has had elbow surgery, has a touchy back and has never won more than 14 games in a season.

The National League West is one screwed-up division.

It's there for anyone's taking. But no one has put together a team that looks like it's a clear winner. The defending champion Giants have to deal with an ace (Jason Schmidt) who probably will start the year on the disabled list, along with their closer (Robb Nen). And their pitching was weak to begin with. Can Barry Bonds do it alone? Arizona has more hitting with Richie Sexson on board, but less pitching with Curt Schilling gone. The Dodgers still -- still! -- have no hitting to speak of. Colorado? San Diego? Anyone? Anyone?

No, Zack Greinke isn't ready. Not yet.

Kansas City may have the angle on the rest of the AL Central, but if the Royals are going to win it, it'll have to be without Greinke, one of baseball's best young pitching prospects. Greinke threw all of 11 2/3 innings in spring training -- and looked tired -- before the K.C. brass sent him down to Class AAA. Greinke will make it back up some day, maybe by midseason. At least now he has a better idea of what he needs to do to get back. And it's not allowing opponents to hit .396 like they did against him this spring.

Ivan Rodriguez can make a difference in Detroit. But not that big of a difference.

The Tigers will be better this year, and their new catcher will help. But when a team wins only 43 games, it's hard not to be better. The main problem for the Tigers is still pitching. Jason Johnson (36-58 career, 4.91 ERA) is their ace. He's followed by Mike Maroth (9-21, 5.73 in '03), Jeremy Bonderman (6-19, 5.56), Nate Cornejo (6-17, 4.67) and Who Knows (stats unavailable). That's trouble. The Tigers can only hope to be like the 1946 Boston Red Sox, who went from 71-83 in 1945 to 104-50 and the pennant in '46, an improvement of 33 games, the AL record. That would give the Kitties a 76-86 record -- which, come to think of it, is a better winning percentage than Johnson has.

The Angels are plenty worried about Brendan Donnelly, too.

Donnelly held lefties to a  .199 average last season (and righties to just .202). He struck out 79 in 74 innings. He was going to be a huge part of the Angels' bullpen. But on March 9, while shagging balls in the outfield, Donnelly caught a line drive with his nose, breaking it in 20 places. Three operations later, he still was having major problems with nosebleeds. Doctors now tell him he has to cease all physical activity to allow the nose to heal, which means the Angels could be without his services for at least April, and maybe much longer. A lot of people like the revamped Angels in the AL West. But this is a big blow.

Bobby Crosby is no Miguel Tejada, but he'll be fine.

On Monday, Oakland's rookie shortstop returned after three days off because of a bruised thigh and smacked two home runs against Seattle. That sounds awfully Tejada-like, but it's way too soon to go there. Still, the A's love what they see from Crosby, which is one of the reasons they felt they could let Tejada go in free agency. (Other reasons being he was too expensive and they were saving the money for Eric Chavez.) Crosby has played a ton this spring, hitting .346 with an OPS above 1.000 while flashing a little leather. In short, the shortstop has done everything asked of him. He'll struggle -- he's only 24 -- but he'll be fine.

Joe Mauer is no superstar yet, either, but he's on his way.

The promise the Minnesota catcher holds made All-Star A.J. Pierzynski expendable, and we are starting to see why. It's not so much the numbers -- though .310, with an OPS near .900, is pretty darn good. More, it's his poise handling the pitchers and at the plate. He simply looks ready. Sure, he'll stumble as the season drags on and opposing pitchers exploit his weaknesses. But the first overall pick in the 2001 draft has shown he has everything it takes to handle the job.

Much as you try, you can't learn much of anything in spring training.

Through Wednesday, the Milwaukee Brewers have the best winning percentage in the Cactus League at 17-12 (.586). The Philadelphia Phillies, who many favor to unseat the Atlanta Braves in the NL East, have the worst record in the Grapefruit League at 10-18 (.357). Enrique Wilson, that replacement-level second baseman for the New York Yankees, is hitting .374, the best mark in the American League (not to mention the Grapefruit League). Marlins outfielder Abraham Nunez leads all players with eight home runs. L.A.'s Odalis Perez is tops with a 0.90 ERA. And I can't believe I just spent all that time looking all that stuff up.

Freaking out

Good thing the Yankees have some spring training games left to play. They're clearly not ready to start the season yet.

I know I'm not the only one with friends who are Yankees fans who freaked out -- went bonkers, I'm telling you -- after that 8-3 Opening Day loss to the Tampa Bay Devil Rays. It's downright funny. I mean, $180 million will buy a lot of things. The best lineup in baseball, for one. But no way does it buy 162 wins.

There are a few Yankees fans ready to jump on Alex Rodriguez already, too. He went 1-for-9 (.111) in the two games in Tokyo. He hit the ball hard in his last couple of at-bats, including a deep fly to center and a line drive to right field. Still, .111 ... I mean, my goodness, bring back Alfonso Soriano!

Which got me to thinking about recent big-name Yankee debuts and how they went. Here are five:

Kevin Brown was solid in his debut, in the second game, giving up six hits, allowing a run and striking out five in seven innings for the win.

Gary Sheffield went 2-for-2 in the Japan opener, with an excuse-me check-swing hit down the right-field line and two walks.

In 2003, Hideki Matsui went 1-for-4 with an RBI in a loss to Toronto. Through his first April in America, he hit .255.

In 2002, Jason Giambi was 1-for-4 with a walk in a win over Baltimore. Giambi hit .282 in his first April in the Bronx, with four homers and 15 RBIs.

Mike Mussina, in his Yankees debut in 2001, pitched 7 2/3 innings of five-hit ball, without allowing a run, in a 1-0 win over the Royals. He struck out three and didn't walk a batter.

Camping out

It's been 30 years since Dr. Frank Jobe fixed ol' Tommy John's elbow, and the Dodgers honored their longtime team physician with a ceremony Wednesday night at Dodgertown. According to the Dodgers, somewhere around 75 major league pitchers have undergone Tommy John surgery since Sept. 25, 1974, when Jobe fixed John. ... Among the teams that are better, but not nearly good enough, heading into the season: the Orioles, who have added Javy Lopez, Rafael Palmeiro and Tejada but still have a rotation consisting of Sidney Ponson, Eric DuBose, Kurt Ainsworth, Matt Riley and Erik Bedard. Ooooof. ... There is some mystery, as manager Ken Macha seems to like it, in Oakland's camp about first base. As in, who will be playing there? The choices are Erubiel Durazo, Scott Hatteberg and Eric Karros, but Macha says this is not a platoon situation. On Opening Day Karros will get the start because the Texas Rangers are pitching lefty Kenny Rogers, and Karros hit lefties to the tune of .366 last season. He's a .316 hitter against southpaws in the past three seasons. ... The A's, by the way, undoubtedly will start the season with a rookie double-play combo, featuring Crosby at shortstop and Esteban German at second. German will take over for Mark Ellis, who will miss at least several weeks -- and possibly the entire season -- with a separated shoulder he suffered in a collision with Crosby. ... Florida's Juan Pierre is just 1-for-15 since returning from a dislocated right pinkie. ... There are a lot of schlock baseball books out there, but I'm looking forward to The Meaning of Ichiro: The New Wave from Japan and the Transformation of Our National Pastime. The book is written by Robert Whiting, a Japanese baseball expert and the author of the bestseller about Japanese baseball, You Gotta Have Wa. Whiting said he did more than 100 interviews, read almost 100 books and traveled more than 100,000 miles in researching the book.

John Donovan is a senior writer for SI.com.