Tomorrow is the difference.
In December, when the Phillies signed Cliff Lee to be their fourth ace, we knew what it meant. We knew the Phillies would have four number-one quality starters to throw against their competition. But until tomorrow night, we won't really feel the difference Lee's signing makes.
After all, for the last two months of the 2010 season, we grew used to seeing three aces take the mound for the Phillies -- Roy Halladay, Cole Hamels, and Roy Oswalt. Other teams went through, in the best case scenario for them, their top three pitchers, seeing a decline with each one. The Phillies, on the other hand, got three virtuoso performances in a row.
And, so far, that's what's happened this season. The Phillies have received excellent starting pitching from Halladay, Lee, and Oswalt, while the Astros threw their top three starters against the Phils. Unlike the Phillies though, the Astros saw a decline in performance with each starter, while the Phillies did not.
But that's the same as last year. Tomorrow night, when Cole Hamels takes the mound against the Mets, we see the difference. The Mets will throw Chris Young against the Phillies. Young has had some good seasons in the past, but he has started a total of 18 games in the past two years because of injuries. Over those 18 games, he has a 4.31 ERA and 1.37 WHIP. That's not bad, but compare that to Hamels' last 18 games, in which he had a 2.28 ERA and 1.04 WHIP.
In fact, comparing Hamels' 2010 to the other NL fourth-game starters shows just what an advantage the Phillies have. The 16 starters are ranked by Baseball Prospectus' 2010 WARP, which is wins above replacement player. Each starter's overall ERA and WHIP in 2010 are also shown, along with games started last year:
| Pitcher | Team | GS | ERA | WHIP | WARP |
| Hamels | PHI | 33 | 3.06 | 1.18 | 5.3 |
| Sanchez | FLA | 32 | 3.55 | 1.34 | 3.6 |
| Kuroda | LAD | 31 | 3.39 | 1.16 | 3.2 |
| Wells | CHI | 32 | 4.26 | 1.40 | 2.3 |
| Zito | SF | 33 | 4.15 | 1.34 | 1.7 |
| Happ | HOU | 16 | 3.40 | 1.37 | 1.3 |
| Narveson | MIL | 28 | 4.99 | 1.38 | 1.0 |
| Young | NYM | 4 | 0.90 | 1.05 | 0.9 |
| Leake | CIN | 22 | 4.23 | 1.50 | 0.5 |
| Beachy | ATL | 3 | 3.00 | 1.53 | 0.2 |
| Harang | SD | 20 | 5.32 | 1.59 | 0.1 |
| Marquis | WSH | 13 | 6.60 | 1.70 | -0.3 |
| Galarraga | ARI | 24 | 4.49 | 1.34 | -0.4 |
| Rogers | COL | 8 | 6.13 | 1.67 | -0.5 |
| Lohse | STL | 18 | 6.55 | 1.78 | -0.8 |
| Morton | PIT | 17 | 7.57 | 1.73 | -1.3 |
Hamels is head and shoulders above the other fourth starters. And that is the difference signing Cliff Lee really makes for the Phillies this year.