On the way to October, little bruises can creep up and turn into big bummers if you don't watch out.
It could be a banged-up bullpen, a couple of hitters who need to bust out of slumps, or a starting pitching staff that needs a breather or three.
And then there's the old non-displaced-compression-fracture-in-the-navicular-bone-of-the-right-foot problem.
The Week Ahead in Major League Baseball promises us another seven full days packed with pennant-race drama. It also reveals some hairline cracks in the armor of some teams who appear to be on their way to the postseason.
Boston is first.
The Red Sox are feeling pretty good about themselves atop the American League East, with a comfortable path to the playoffs. But outfielder Jacoby Ellsbury, whose bounceback season has been one of the keys to Boston's resurgence, is headed to Denver to get a second opinion on the foot injury that came along with 17 games left in the regular season.
The Red Sox are entering a nine-game stretch beginning on Tuesday in which they play the other top three teams in their division. They'll play three at Tampa Bay and three at home against the Yankees this week. Boston will begin to prepare for October while hoping -- and as it turns out, expecting -- that Ellsbury and his game-changing speed and lineup presence will be back soon.
"We feel like he'll be back to us before this year is out," Boston manager John Farrell said. "We're hopeful in the regular season, yes."
Hopeful is a good word. Even for the clubs cruising with huge division leads (we're looking at you, Red Sox, Tigers, Braves and Dodgers) and especially for Wild Card teams on the brink, the week ahead is a big one. For others, it is the biggest week of the year.
In the AL, the Orioles, Indians, Yankees and Royals are all in Wild Card play and all are within 3 1/2 games of the Rays and Rangers, who are the clubhouse leaders for the single-elimination game.
But in the National League, Washington (eight back) and Arizona (nine back) are in danger of falling out of Wild Card contention for good if they have bad weeks.
The Nationals will spend this crucial week playing in their division, the NL East, when they visit New York for four games against the Mets before returning to Washington, D.C., to host the Phillies for a weekend three-pack.
The Nats mostly won't be at full strength on Monday, because outfielder Bryce Harper is visiting a team physician to have his sore left hip looked at.
But somehow they need to get hot or they'll be going home at the end of the month, though Sunday's 6-4 win over Miami was a good way to preface the week.
"I liked the way our lineup's swinging the bat," Nationals manager Davey Johnson said. "We just need to continue. We can't afford to have any lapses. We've got to win them all."
The same goes for Arizona, which will play three against the Dodgers in Los Angeles and three at home over the weekend against Colorado and has to break out of a recent offensive funk -- they're averaging 2.2 runs per game over their past 11 -- to make any kind of noise before it's too late.
"We're not in a good streak right now," manager Kirk Gibson said. "Part of it is baseball, part of it is pitching. It's part of the game. We'd certainly like to be better than we've shown."
Meanwhile, it wouldn't be unwise to expect some of the best baseball to be played this week to come from the teams embroiled in the tightest division races.
Entering Monday, Oakland led Texas by a mere 1 1/2 games in the AL West, and St. Louis had but a 1 1/2-game lead on Pittsburgh and Cincinnati, which are in a virtual tie for second place in the NL Central.
The A's, who have won three in a row, get three games in Minnesota against the Twins before a weekend showdown in Arlington against -- who else? -- the Rangers.
It will be the last time the two clubs meet in the regular season.
"There's a combination of some good things happening right now," Oakland manager Bob Melvin said. "It just seems like this is a very good stretch for us when you think back to our body of work throughout the whole season."
Then again, the A's will have to face the Rangers on the road this time, and Texas will be ready. The Rangers beat the Angels in Anaheim on Sunday to snap a three-game losing streak and will get a stern test at home prior to the A's series by meeting the Pirates for three games.
"Right now every win is important; we are playing for the pennant," Rangers outfielder Alex Rios said. "What we did today in coming from behind was great. Hopefully it will boost our confidence and keep us going."
The Cardinals routed the Pirates in St. Louis on Sunday, and since Pittsburgh guaranteed itself a non-losing record for the first time in 21 years earlier last week by notching its 81st victory of the season, it has not annexed the all-important No. 82 that will represent the first winning campaign for the team since 1992.
Of course, that's a silly technicality, but Pittsburgh has to play better with St. Louis finding its stride and the Reds right there with them. The trip to Texas figures to be a difficult one, and the Pirates will finish the week with four at home against the struggling Cubs.
"You know what? We'll be out of St. Louis tomorrow, in Texas," Pirates manager Clint Hurdle said. "We got to go play. The season doesn't stop, and we got every opportunity to get back to rolling things in a good way.
"We know what we need to do. We'll round up [Monday] for the first game of a series in a new town."
Doug Miller is a reporter for MLB.com. Follow him on Twitter @DougMillerMLB.