Who is Edwin Jackson?

PHILADELPHIA – Is Edwin Jackson the guy who went 1-8 with a 6.29 ERA in his first 11 starts as a Cub?

Or the guy who went 6-3, 3.13 in his next 10 – including 3-1, 1.83 in five July starts?

And how does either one explain what happened Tuesday night in a 9-8 loss to the Phillies at Citizens Bank Park in the opener of a three-game series?

It’s the $52 million question for the Cubs, who invested a four-year contract in the free agent last winter and thought they were getting something a little steadier for the money.

“He’s getting some late action [on his fastball]. He’s got a ratio of ground balls to fly balls like a power-type-sinker guy right now,” manager Dale Sveum said after Jackson’s last start in the 10-game surge. “It’s kind of off the charts for a guy not like Derek Lowe or Kevin Brown or [Jake] Peavy, guys that make their living on ground balls. And he’s not walking anybody, so his efficiency’s better.”

By Tuesday, the sink was gone again, and the offensively struggling Phillies raked him for 10 hits in five inefficient innings as Jackson blew early 4-1 and 5-2 leads. He also walked a pair and escaped worse damage only because of a couple line-drive outs, including an inning-ending double play in the first.

“He was getting some pretty good contact, obviously,” Sveum said.

Jackson, who had said he wasn’t doing things so much differently as getting different luck during his streak, said Tuesday he was out of rhythm in what he called a “grind start” where he had to fight through not having his best stuff.

So is he the hard-hit, perhaps hard-luck, pitcher who got booed by Wrigley fans during that rough 11-game start to his season? Or the guy who followed with the streak?

“I worked too hard to get back to form to let one game bring me back down,” he said. “I had a good little stretch and I’m definitely not trying to let this game get in my head to mess up what I had going on.”

So who is Edwin Jackson? It might take the final nine weeks of the season to try to answer that for 2013 — never mind the bigger, four-year, $52-million question.