Chicago ? After their dismal display in the first half, the Chicago White Sox weren’t even in the background of the playoff picture.

They weren’t hitting. Their pitching was shaky. They couldn’t beat the lowly Detroit Tigers.

“We played so bad the first half,” Frank Thomas said. “You couldn’t play any worse than we played in the first half.”

Yet here they are, shaking up the American League Central race with an early second-half tear. A major league-best 15-5 since the All-Star break, the White Sox have made up six games on Kansas City and are now just a half game behind the division leaders.

“Honestly, there’s no explanation,” Paul Konerko said. “I can’t figure it out — and I don’t want to. I just want to have the team keep going the way it is, and, hopefully, we’ll win this thing.”

The White Sox were off Thursday before beginning a three-game series with Oakland.

On paper, the White Sox were supposed to be one of the American League’s top teams. They’d traded for Bartolo Colon, pairing him with Mark Buehrle for one of the most formidable 1-2 combinations in the AL. They’d bolstered their bullpen by getting closer Billy Koch.

And Thomas, Konerko, Magglio Ordonez and Carlos Lee gave them an offensive juggernaut few teams could match.

But the White Sox didn’t live up to the hype, bumbling through April and May. Colon, Buehrle and Koch scuffled, and Ordonez, Lee and Konerko struggled to find their hitting strokes. Manager Jerry Manuel’s job seemed to be in jeopardy.

“Everything went bad,” Thomas said.

When the White Sox lost to Los Angeles June 6, they dropped a season-low eight games under .500 and 81/2 games back.

They got a little boost from the annual Crosstown Series, taking four of six from their North Side rivals, the Cubs. They took five of six from the Twins, too, and suddenly found themselves three games back July 2.

Convinced his team could make a run at the playoffs, general manager Kenny Williams made two big moves. First he traded for Roberto Alomar. A few hours later, he got Carl Everett.

“It added a little shot of adrenaline,” Thomas said. “That gives us more ammunition. I think it just made it easier on everyone’s confidence.”

After taking two out of three in a home series against the Royals this week, they moved within a game of Kansas City.