With the announcement that the Philadelphia Phillies had signed Cliff Lee late Monday night, the baseball world began to contemplate whether a starting rotation consisting of Lee, Roy Halladay, Cole Hamels, and Roy Oswalt was perhaps the greatest in the history of the game.

When most of us think about the best pitching rotations, we tend to point to the Oakland A's of 2001-2003, the Atlanta Braves of the 1990s, the New York Mets of the 1970s, the Los Angeles Dodgers of the 1960s, the Cleveland Indians of the 1950s, or maybe the 1971 Baltimore Orioles if you're into wins.

In the Greatest Starting Rotations of All-Time, Andrew Johnson of Fanhouse writes, "Only 25 pitching staffs since 1901 have ever boasted four or more pitchers who qualified for the ERA title with an ERA+ equal to or greater than 120, according to Baseball-Reference.com." He highlights six rotations and includes a link to his Play Index findings.

At the Baseball Reference blog, Steve Lombardi ups the ante a bit, creating a post on teams with four starting pitchers with at least 30 GS and ERA+ of 130 or above. It's happened just once: the 1997 Atlanta Braves with Tom Glavine, Greg Maddux, Denny Neagle, and John Smoltz. He includes a link to his Play Index results as well.

Dave Cameron of Fangraphs uses Wins Above Replacement (WAR) totals for the past three years to determine where the Phillies Big Four stacks up in Best. Rotation. Ever? Halladay (21.5) ranks No. 1, Lee (20.9) No. 2, Hamels (11.9) No. 16, and Oswalt (11.2) No. 21 for a cumulative total of 65.5. The 1993 to 1995 and 1996 to 1998 Braves featuring Maddux, Glavine, Smoltz, and Steve Avery/Neagle totaled 56 and 66.8, respectively. Maddux's three-year totals exceeded Halladay's, Smoltz's '96-'98 run fell just shy of Lee's, Glavine's '93-'95 is slightly worse than and his '96-'98 is superior to Hamels', and the fourth starter of Avery or Neagle is worse than Oswalt's totals.

With respect to Avery and Neagle, Cameron adds, "That was part of what made that Braves run so spectacular. They kept swapping out guys behind The Big Three and getting high-level performances even with all the changes. There were times where they got equivalent production to what we might expect from Philly’s rotation in 2011, but they never had four guys who had established themselves at this level going into a season."

In conclusion, Cameron says:

If there’s a four-man rotation that has ever looked this dominant heading into a new year, I can’t find it. It is almost certainly in the discussion for the greatest four-man rotation of all time.

Taking a slightly different approach, my brother Tom forwarded to me the following table from Baseball-Reference's Play Index. It is a list of all the teams with four starting pitchers in the rotation generating at least four WAR while qualifying for the league ERA title. Seven teams made the cut, including the Braves in 1991 (without Maddux) and 1997. Aside from those Atlanta staffs and the 1967 Cincinnati Reds, you have to go back almost 100 years to find a 4x4 rotation.

Note: Pitching WAR differs between Fangraphs and Baseball-Reference in that the former uses Fielding Independent Pitching (FIP) and the latter uses Sean Smith's defense-adjusted Run Average.

Wanting to drill down deeper to look at the individual and cumulative totals produced the next table.

There are several interesting observations:

1. The 1912 Pittsburgh Pirates had four pitchers with at least four WAR but none with five. A very solid 1-4 but no real ace.

2. The 1909 Philadelphia A's had four pitchers with at least four WAR but none with more than five. These four starters, including Hall of Famers Chief Bender and Eddie Plank, had ERAs of 1.76 or below. It wasn't known as the Deadball Era for nothing. The league average ERA was 2.47. The league-wide run average was 3.44. Lots of errors back then. Despite the smaller gloves, the official scorekeepers held the fielders to a high standard.

3. The other five staffs all had at least one starter with a WAR of six or more. Of those five, two had three pitchers with at least five WAR.

4. The Braves, in a couple of different renditions, had the best starting four as measured by B-R WAR since the early part of the last century.

5. Led by Joe Wood, the 1912 Boston Red Sox had the most productive staff among those teams with 4x4 since 1900. With 9.6 WAR, Wood had the highest single-season total among all the pitchers on this list. Furthermore, the Red Sox had the highest four-man, single-season cumulative WAR at 24.1.

How does the Phillies staff compare to these all-time great rotations? Last year, the foursome produced 21 WAR (although not on the same team). Halladay had 6.9, Oswalt 5.1, Hamels 4.7, and Lee 4.3. Oswalt split his WAR among the Houston Astros (2.3) and the Phillies (2.8) while Lee split his among the Seattle Mariners (2.6) and Texas Rangers (1.7).

If these Philadelphia starters can repeat their 2010 performance, the Phillies could surpass the Braves and become the greatest four-man rotation since Smoky Joe and the 1912 Red Sox, at least as measured by Baseball-Reference's Wins Above Replacement.