When Adam Wainwright hurt his Achilles while batting in late April, it was thought his absence would hurt the St. Louis Cardinals rotation. Certainly, in a division as tight as the National League Central, with teams like the Pittsburgh Pirates and Chicago Cubs giving them a run for their money, the Cardinals would need to replace the ace they lost with another ace.

Fast forward to now. The Cardinals are still without Wainwright (as they will be for the rest of the season), but instead of faltering, their rotation is thriving. Coming into Sunday, St. Louis pitching had not allowed a run in 36 straight innings.

Well on Sunday, they did give up a run. In fact, they gave up five of them in a 5-4 loss to the Milwaukee Brewers. But even with that defeat, the Cardinals starting rotation can still boast being the best in baseball at the moment.

Through Sunday's games, their 2.77 ERA is far and away better than the next closest team, the Oakland A's. Their 12.5 fWAR is tied with the Dodgers for most in the Majors, their .238 batting average against is tied for third-best, and their 610 strikeouts is fourth-best. 

All this without Adam Wainwright. So how are they doing? Or, more to the point, who is doing it?

Aside from the injury to Wainwright, the rest of the Cardinals' rotation has remained healthy and consistent. Lance Lynn has been their best starter, according to FanGraphs' Wins Above Replacement and our John Lackey's contract stipulated that he make the league minimum this season, thanks to suffering a serious injury during his time in Boston that was related to an even earlier injury? Confused? I don't blame you. All that means is that the Cardinals have gotten 2.5 fWAR out of Lackey and a 2.85 ERA in 22 starts for the low-low cost of just over $500,000 this season. He's having his best season since 2009 when he went 19-9 with a 3.01 ERA for the Anaheim Angels, with a 5.0 fWAR. Interestingly, none of his peripherals look any different than the last few seasons, except for his home run rate, which is the lowest it's been since 2006.

There was no guarantee Michael Wacha was going to be able to make it through the entire season unscathed, let alone be second on the team in fWAR at 2.7. When he burst onto the scene as a rookie in 2013 and dominated the postseason, he did so while striking out a little more than a batter per inning. Here in 2015, his first full season since coming back from a shoulder injury, he's striking out fewer hitters, down from 9.05 in '13 to 7.62 per nine innings now. He's also throwing fewer fastballs (down from 64.9% of his pitches in 2013 to 56.7% this year) and changeups (27.4 to 16.4%), while increasing the use of his cutter (2.7 to 15.8%) and curveball (5.0 to 11.1%). That has resulted in softer contact (19.6% of balls hit off him were considered soft contact by FanGraphs, compared to 11.9% in 2013), and his hart-hit percentage has fallen from 35.8 to 29.3%. 

And in his first full season as a starter, Carlos Martinez is living up to the hype many predicted for him. He leads all St. Louis starters in strikeouts per nine (9.27), with a fastball that averages about 95 mph as well as a devastating slider and change-up. He turns 24 at the end of the year, and appears to be a top-of-the-rotation arm for years to come.

St. Louis has also recently welcomed back Jaime Garcia from the disabled list, a big deal considering he is the only left-hander in the rotation. Obviously, having a rotation of all righties hasn't been a problem for the Cardinals, so perhaps the importance of lefty-righty balance is overstated. Nevertheless, Garcia has pennant race and postseason experience, and has performed well since coming off the DL, with a 3.27 ERA in 10 starts.

The New York Mets rotation gets talked about a lot, and the Los Angeles Dodgers certainly have the best 1-2 punch in the game. But top to bottom, it's going to be hard for any team to match up with St. Louis one through four once October rolls around.