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Zambrano an Ace?

Next year has arrived in Chicago, and with Rich Harden gone, even more pressure will be on starter Carlos Zambrano to carry a heavy load for the Cubs rotation. His season did not get off to a good start yesterday, as he was lit up for 8 runs in only 1.1 innings, including home runs by Jason Heyward and Brian McCann. For the Cubs to challenge the Cardinals for the Central division title, Zambrano will have to pitch like an ace, as without him, the Cubs are likely a sub-.500 team.

Unfortunately, Zambrano certainly hasn’t been an ace pitcher over the last four years. Since 2006, his xFIP hasn’t been outside the 4.20-4.65 range, and only a stupidly low 5.6% HR/FB rate managed to get his 2009 FIP to 3.61. It’s really quite simple – Zambrano walks too many to be an ace at this point. 2008 was the only time in the same four year stretch in which Zambrano managed a walk rate below 4.00 per nine innings.

Somehow, though, Zambrano has managed to post ERA’s under 4.00 for all of the aforementioned years – in large part relying on BABIPs lower than .280. Zambrano has pitched for three above average defensive teams (from 2006 to 2008). Last season, the Cubs fell to a below average team UZR, and Zambrano’s BABIP skyrocketed to .308. Although that is by no means conclusive, it is possible that solid fielding behind him is in part responsible for Zambrano constantly outperforming his FIP. If that has disappeared this year, Zambrano could be in trouble.

There may be some heavy regression in line for Zambrano – both in terms of career BABIP and in terms of home runs allowed – and Monday may only have been the beginning. Zambrano should still be an above average pitcher, but he no longer has the ability to constantly win games by himself that the true aces do. If Zambrano doesn’t have the position players playing great baseball behind him like the Cubs had in 2006 and 2007, the Cubs will be on the outside looking in come September and October.