It’s been quite a week for White Sox rookie Alexei Ramirez, the 26-year-old Cuban émigré who signed a four-year deal during the offseason. It was uncertain whether Ramirez was ready to stick with the White Sox in spring training, or would need some time in the minors.

That question’s been answered over the course of the season, and Ramirez put an exclamation point on the answer this week. The rookie middle infielder, who turns 27 on Monday, stroked four home runs in the last seven days, including a grand slam Friday in a 9-4 win over Kansas City. The slam was his third of the season to tie a major league record for rookies, and by recording the team’s 11th slam of 2008, allowed the White Sox to tie the franchise’s single-season record.

Ramirez connected on another home run Saturday, and that gave him 20 on the season. Going into Sunday’s series finale with the Royals, he is batting .297 with 72 RBIs in 127 games.

The White Sox have received quite a payoff on Ramirez, who may move from second base to shortstop in 2009. As a middle infielder, he would give the team better-than-average production at either position.

It would have been difficult to forecast Ramirez’s success after the rookie struggled during the opening month of the season. He was 4-for-33 (.121) through the end of April. He had scored just one run and driven in two in his first 14 games.

Since then, Ramirez is batting .311 with 20 homers and 70 RBIs. Among rookies with at least 250 plate appearances since May 1, he trails only the Royals’ Mike Aviles (.321) in batting. During this span, only Tampa Bay’s Evan Longoria (22) and Cincinnati’s Jay Bruce (21) have hit more homers. Only Longoria (72) has more RBIs.

For the season, thanks to his post-April performance, Ramirez ranks fifth among rookies in both homers and RBIs. After a poor start, he has worked himself into the mix for Rookie of the Year consideration. Although Longoria seems to be the front-runner, Ramirez has turned in a first season that is as remarkable as it was unanticipated. Where would the White Sox be without adding Ramirez and Carlos Quentin to the mix in 2008?