Halladay. Lee. Hamels. Oswalt.

There’s been a lot of ink spilled this week about the new Phillies rotation, featuring their “four aces”. After signing Roy Halladay last year and then trading for Roy Oswalt (who caught fire after the deal), people were already talking about how great Philadelphia’s rotation was. But, with the Cliff Lee signing the other day, the rhetoric exploded. Now you can’t go anywhere without reading about how great the quartet is.

The value of having four aces is almost too obvious to mention. By being able to pitch a viable top of the rotation starter every four out of five days, the Phillies will never let up on their opponents. “Great, you don’t have to face Roy Halladay. How nice. But now you have to deal with Cliff Lee. Nice consolation.”

But the biggest advantage comes at the back of the rotation. In a normal series, when the opponent is pitching his number four starter, than the team is also throwing his number four starter. So Kyle Lohse gets to match up with Manny Parra. When you have four aces, though, that Lohse/Parra match-up becomes Hamels/Parra without sacrificing an ace-on-ace matchup two days later. That’s a huge benefit for the Phils.

(Click “Read More” to continue reading (and for tables!).)

Occasionally, team rotations don’t match up all that well and we find a true number one matching up with a number four (for example). If this were to happen to this year’s Phillies, the opponent would get no advantage since they’d be facing Cole Hamels and not Kyle Lohse or Manny Parra.

Thinking about these back-of-the-rotation advantages for the Phillies, I started wondering just how often these various scenarios crop up. Using the 2011 schedules from MLB.com, I did a little fooling around. Making some really simple assumptions – that teams will always start their five pitchers in order without skipping a start and that all teams will re-start their rotation following the All-Star break – I matched up all teams against each other to find out who the expected starter is for every game. As you might expect, the number ones match up with the number ones most often, the number twos with the number twos, and so on. In the cases where they don’t, it’s usually only one rotation spot away (eg, the numbers ones with the number twos or the number fives).

But it isn’t always that simple. The table below shows the average number of starts each team’s rotation spot faces off against their opponents’ rotation spots. For example, an average team’s number two starter (on the left) starts seven games against their opponent’s number three starter (on the top).

Average Starts between Rotation Spots, MLB-wide 2011

Opponents’ Rotation Spot 1 2 3 4 5 1 16.2 6.9 1.6 1.6 6.8 2 6.9 16.3 7 1.5 1.3 3 1.6 7 14.8 7.2 1.5 4 1.6 1.5 7.2 14.5 7.2 5 6.8 1.3 1.5 7.2 15.1

The Phillies chart is pretty similar to the average. It seems to be a little top-heavy, with the number one spot facing more of his opponents’ aces than other teams. The eighteen games where the number three and four Phillies pitchers face off against opponents’ one, two, and three starters should work well for the Phils.

Number of Starts between Rotation Spots, 2011 Phillies

Opponents’ Rotation Spot 1 2 3 4 5 1 (Doc) 17 10 0 1 6 2 (Lee) 7 14 10 1 0 3 (Oswalt) 0 7 14 9 2 4 (Hamels) 2 1 8 12 8 5 7 1 1 7 16

There are plenty of other ways to play with these schedules, and I might just do that over the next couple of days. In the meantime, though, it’s nice to see one likely way these “four aces” will be utilized. It’s almost impossible to be down on this group.

So, what do you see in these charts?