How Much Better Do Lee & Ludwick Make The Pirates?

The Pittsburgh Pirates made 2 moves at the deadline, acquiring Derrek Lee and Ryan Ludwick. It is now Monday and both of those guys are in the lineup. Let's compare these two to the players that they are replacing. I'm going to use ZiPS in this comparison, which basically is a tool that predicts the stats that each player will contribute for the rest of the season.

Lyle Overbay vs. Derrek Lee:

Overbay: .227/.300/.349, 8 HR, .290 wOBA, -0.8 WAR, -5.3 UZR
Lee: .246/.302/.404, 12 HR, .310 wOBA, 0.5 WAR, 5.3 UZR

Overbay ZiPS: .240/.323/.401, 5 HR, .320 wOBA
Lee ZiPS: .264/.335/.434, 7 HR, .337 wOBA

Garrett Jones vs. Ryan Ludwick

Jones: .230/.315/.404, 10 HR, .317 wOBA, 0.8 WAR, 2.4 UZR
Ludwick: .253/.301/.373, 11 HR, .298 wOBA, 1.0 WAR, 2.1 UZR

Jones ZiPS: .253/.316/.433, 7 HR, .327 wOBA
Ludwick ZiPS: .253/.319/.416, 6 HR, .321 wOBA

The upgrade is more substantial at first base, obviously. In fact, ZiPS shows that going from Jones to Ludwick is a downgrade, however that doesn't factor in the ballpark change for Ludwick, which really could make a huge difference in this situation.

I also ran some lineups tests. I used Baseball Musings' Lineup Analysis Tool to compare the run expectancy per game for the two lineups pre-trades and post-trades. I used the ZiPS numbers for this test. So these numbers are the runs per game these two lineups would be expected to put up for the rest of the season. I assumed that Alex Presley would be making the majority of the starts in left field and used his expected stats in both cases.

Lineup with Lee & Ludwick: 3.968 runs per game
Lineup with Overbay & Jones: 3.920 runs per game

So according to that test, the new lineup is .48 runs per game better than the old lineup. When you stretch that out to the remaining 57 games, the Pirates will score 27.36 more runs then they would have had they not made the trades. If you take the common sabermetric belief that 10 runs gained/saved equals 1 win, the Pirates have gotten themselves 2.736 more wins for the rest of the year. This probably isn't the ideal way to do this kind of test, and I'm questioning whether these two upgrades really improved the team by 2 wins, but it sure sounds good, doesn't it?