Chicago Cubs manager Dale Sveum has compared Javier Baez’s bat speed to that of nine-time All-Star Gary Sheffield’s vicious swing.

Even Sheffield, who finished with 509 career home runs, would be impressed with what the 20-year-old Cubs shortstop prospect has done over the last two days.

Baez has hit four home runs in his last five at-bats on a total of seven pitches, including two off Bruce Chen on Saturday as a Cubs split-squad pounded out an 8-3 win over the Kansas City Royals.

“I am seeing the ball pretty good and hitting the ball hard,” he said. “This is my first time, and it feels great.”

Baez has received an extended look because shortstop Starlin Castro missed 12 games due to a leg injury before recently returning, and now the Cubs are in the middle of three straight split-squad days.

Baez was the Cubs’ first pick — ninth overall — in the 2011 draft and is expected to be sent to minor-league camp in the coming days, but not before giving a glimpse of what he can do.

“That’s not my decision, so I will do whatever they want me to do,” said Baez, who is hitting .324 with four home runs and eight RBIs in 34 at-bats.

Joining Baez in the hitting barrage were David DeJesus, who led off the bottom of the first with a home run, Alfonso Soriano, who hit a two-run shot in the first, and second baseman Alberto Gonzalez, who connected for a solo shot in the fourth.

Chen, who is competing with three others for the fifth sport in the rotation, was roughed up by the Cubs as they hit five home runs, including three in the first inning, off the veteran left-hander.

In five innings he allowed nine hits, seven runs — six earned — with one walk and four strikeouts while facing 25 batters.

“I feel like I made some adjustments after the first inning,” Chen said. “I made some good pitches and some bad pitches. Overall, I need to improve and make better pitches. My body felt good and I just need to work on keeping the ball down.”