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8/8/2014 8:41 P.M. ET

There's no such thing as a perfect team

A roster built with the biggest payroll in Major League Baseball history appears to be paying off for the Dodgers. They're sitting atop the National League West, sporting a league-best 66-50 record going into the weekend and starting to pull away from the Giants.

But as good as the Dodgers have been, there are concerns with them and just about every other postseason contender in baseball.

The Dodgers have a dominating Big Three with Clayton Kershaw, Zack Greinke and Hyun-Jin Ryu. But they had two question marks in the rotation that were concerning enough for them to pick up veteran Roberto Hernandez from the Phillies to start against the Brewers on Friday. Unwilling to give up top prospects for David Price before the Trade Deadline, the Dodgers had a need for a strong No. 4 to make a deep run in postseason. Dan Haren pitched 7 1/3 innings of one-run ball to beat the Angels on Thursday, but he had given up 26 earned runs in 23 1/3 innings in his five previous losses. Josh Beckett tried to pitch through a torn labrum in his left hip, but it didn't work and he was placed on the 15-day disabled list, retroactive to Monday. He worked only 12 innings, giving up 11 earned runs, in three starts over the past month, and he hasn't worked more than five innings since the end of June.

The Brewers have had at least a share of the NL Central lead since April 5, but it's been a challenge lately. Entering Friday's action, they've lost 20 of their past 32 games, compiling a 4.06 ERA, which ranks 11th in the NL. The rotation does have 19 quality starts during that stretch, but the bullpen has blown five out of 12 save chances, is 1-7 and has a 4.39 ERA. Only the last-place NL teams (the Cubs, Phillies and Brewers) have had a higher bullpen ERA in that span.

The Nationals made a move this week to fill their left-handed late-inning role, and they received Matt Thornton on a waiver claim from the Yankees. Thornton worked 1 2/3 scoreless innings on Wednesday and Thursday, helping calm a bullpen that had allowed 18 earned runs in 21 2/3 innings since July 28 before his arrival. He also lessens the burden on converted starter Ross Detwiler, whom the Nationals don't want to throw into a late-inning spot, and struggling Jerry Blevins, whose ERA has risen from 3.15 to 5.05 since late May.

The Cardinals beefed up their rotation at the Trade Deadline, but the defending NL champions continue to struggle offensively. They've averaged 3.47 runs per game, which is better than only four NL teams since the All-Star break. Matt Adams (.313, fourth) and Matt Carpenter (.284, 20th) are the only Cardinals players among top 20 in NL in hitting. They don't have a player among the top 40 in RBIs, and Jhonny Peralta (15 homers, tied for 19th) is the only hitter among the top 30 in home runs.

Even though he's not on the disabled list, the Pirates lost their catalyst, Andrew McCutchen, to a fractured rib. Don't be blinded by the Pirates' 94 runs scored since the break, which is tied for first in the Majors. The Bucs are a team built on pitching, which only adds to their need for a strong defense. And that's a problem. Pittsburgh ranks 14th in the NL with a .982 fielding percentage. Nobody has struggled more than third baseman Pedro Alvarez, whose erratic throwing has led to a Major League-high 24 errors and a .925 fielding percentage, raising questions about a possible move to first base.

The Giants got Angel Pagan back in center field on Thursday, which should be a boost. They were 19-26 when he was sidelined with a bulging disk in his lower back. But the Giants' recent success has been built on their rotation, and there are growing concerns in that area. Madison Bumgarner (13-8) and Tim Lincecum (9-7) are the only starters with a winning record, and Matt Cain will undergo surgery on Monday to remove bone chips from his right elbow. The Giants hope a reunion of manager Bruce Bochy and Jake Peavy will rejuvenate the right-hander. But Peavy has lost his three starts since being acquired from Boston, and he hasn't won since April 25.

The Reds have been hit hard with injuries, including losing Brandon Phillips and Joey Votto for an extended period on the DL. It's hard to see them being able to remain a factor in the NL Central or Wild Card if they don't find an offensive lift. They're ranked 28th in baseball with 62 runs scored and 29th with a .326 slugging percentage since the All-Star break.

The Braves are dealing with a young lineup in which no regular is 30. They've fallen 4 1/2 games back in the NL East and 3 1/2 back of the second NL Wild Card spot. Struggling since the break offensively, the Braves rank 27th in baseball with 64 runs scored and 28th in slugging percentage at .331.

Tracy Ringolsby is a columnist for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.