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3/24/2014 8:41 P.M. ET

Lake looks to springboard off three-homer game

MESA, Ariz. -- Junior Lake said he never had a three-homer game in the Minor Leagues, but he delivered one on Sunday for the Cubs in a Cactus League game against the Athletics.

"I needed that," the outfielder said Monday. "That's why I'm working. I work every day to be prepared for the [big leagues]."

Lake has been getting extra at-bats in the Cubs' Minor League games the last few days, which has helped.

"I can see more pitches," he said. "For me, it's the same pitches in the [Minors as in the] big leagues. The big leaguers are more consistent. I go to the Minor Leagues, and I can see more pitches."

Lake grounded out in the first, tried to bunt in his second at-bat in the fourth inning, and hit his first home run of the spring in the sixth, a three-run shot. He added a two-run homer in the seventh and a solo shot to straightaway center in the ninth.

Which one felt the best?

"The last one," Lake said, smiling.

Lake had swung at the first pitch in his first at-bat, then tried to bunt on an 0-1 pitch. Cubs hitting coach Bill Mueller is encouraging players to go deeper into counts, which Lake did on the home run swings.

"He went back to the drawing board [after the bunt]," Cubs manager Rick Renteria said. "The more he sees pitches, the more it seems like he gets into the rhythm of the at-bat."

Renteria had looked at video of Lake over the winter. The young outfielder, who made his big league debut last season, and batted .284 in 64 games, is listening to Mueller and making progress at the plate.

"I'm not worried about the results. I'm really concerned about their approaches," Renteria said. "I thought [Sunday], he took a big step forward. You've got to do it on a daily basis. Yesterday wasn't a bad step."

Starlin 'really close' to being ready for Opening Day

MESA, Ariz. -- Cubs shortstop Starlin Castro, sidelined since he strained his right hamstring on March 2, celebrated his 24th birthday on Monday by playing in a Minor League game and announced he was "real close" to being ready for the regular season.

Castro did not have a ball hit to him at short, but he was active in the field. At the plate, he got an at-bat every inning, and he delivered an RBI single.

"I feel great, really good," Castro said. "I tried to do all the moving, and I feel pretty good."

"He's getting his baseball feet underneath him," Cubs manager Rick Renteria said, "and we're hopeful his progression is where it needs to be."

What's next? Castro wanted to play in another Minor League game on Tuesday, but he will take batting practice and do some defensive work.

"We're going to push him," Renteria said. "He's going to be very active [Tuesday]."

Opening Day is one week away.

"I got my rhythm, have to stay in my rhythm," Castro said.

How close is he to being ready?

"Really close," Castro said. "I don't know the day now to play in a big league game, but I can say I'm really close. I got a base hit over there and was running hard and turned and felt pretty good, didn't feel anything."

He tested his leg by moving on foul balls, and on balls not hit to him.

"I got a feel for where I'm at and I feel pretty good," he said.

The only thing left is to keep playing.

"It's not the same intensity over there in the Minor Leagues as the big leagues," he said.

As for his birthday, Castro planned to celebrate with family, including his son, Starlin Jr., who will turn 1 year old on Friday.

Whiteside waiting for opportunity to knock

MESA, Ariz. -- The last week of Spring Training can be the longest for players who are not sure if they've made the Opening Day roster. Just ask Eli Whiteside.

"It's been like this for a long time -- several years," Whiteside said Monday.

The 34-year-old is one of four catchers still in Cubs camp, joining Welington Castillo, who will be the regular backstop, George Kottaras and John Baker. Whiteside and Baker were non-roster invitees.

Whiteside saw that Rangers are in need of a catcher, as former Cub Geovany Soto was injured and will be sidelined 10-12 weeks. That creates an opening.

"[The news] is obviously out there," Whiteside said. "If you watch ballgames and that kind of stuff, [the news is] running across the bottom line [of the television]. It's out there and it's noticeable. You just try to come in, get your work in, and do what you can to prove yourself to this team and any other team that's out there looking."

Extra bases

Mike Olt, making his third start at third base Sunday for the Cubs on Sunday, made two errors in one inning. Manager Rick Renteria wasn't concerned.

"I think he's just a little rusty out there," Renteria said. "He's been swinging the bat pretty much all spring. We'll just keep putting him out there and letting him work through it and get comfortable."

The Cubs are still deciding who will get regular time at third base this season. Between Olt, Luis Valbuena and Donnie Murphy, who will start Opening Day?

"I'm not willing to tell you, and we'll let it keep playing itself out," Renteria said.

• Left-handed pitcher Tsuyoshi Wada, who was granted his unconditional release by the Cubs on Sunday, signed a Minor League contract to return to the organization on Monday.

Wada gave up seven runs on 10 hits over 5 2/3 innings in three games, including one start, and will start Tuesday against the Angels at Cubs Park, one of the team's split-squad games.

"He has to continue to improve," Renteria said of the lefty. "His command was a little bit erratic during the course of the spring. He wants to continue to make strides, he wants to continue to pitch and do those things that will help him be effective."

Chang-Yong Lim is headed to Korea. The Cubs sold the contract of the right-handed pitcher to the Samsung team for cash considerations.

• Cubs shortstop Starlin Castro will host a one-day Baseball ProCamp presented by SunnyD On July 22 from 9 a.m.-12:30 p.m. CT at Evanston (Ill.) Township High School. Participants will learn fundamental baseball skills and have the opportunity to meet and interact with Castro. Each camper will receive an autographed item from Castro, and a team photo.

Castro will be joined by a prep and college coaches from the area. The camp is open to boys and girls of all skill levels from grades 1 to 8. Cost is $99. Registration and more information are available by visiting StarlinCastroCamp.com.

Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.