Starlin Castro entered this spring focused on a comeback season.

MESA, Ariz. -- Starlin Castro is running out of time if he is going to be ready by Opening Day.

The Cubs shortstop ran the bases on Thursday for the first time since he strained his right hamstring on March 2, and hopes to get at-bats in a Minor League game on Saturday. He's making good progress, manager Rick Renteria said Friday. But Sunday will be the three-week mark since Castro was injured, and it also marks the beginning of the final week of Cactus League games.

"I think [Saturday] I'll go to the Minor League [game] and get some at-bats -- four, five at-bats -- and hit every inning," Castro said after batting practice on Friday.

Does he have enough time?

"If you go every other day and go to the Minor Leagues and take five at-bats, I think I'll be all right," he said. "I can be there."

The Cubs have not talked to Castro about the possibility of opening the season on the disabled list.

"I don't think that will happen, because I've really progressed and I think I'll be all right," he said.

"We're trying to get him some at-bats, possibly in the Minor Leagues first, leading off, things of that nature, and trying to get him in baseball shape," Renteria said Friday. "He's been doing a lot of activity, but getting him out there, standing, playing five, six innings is important to us. We're going to try to progress him as quickly as possible."

Do the Cubs have a backup plan?

"Not even a consideration at this point," Renteria said. "He's doing well."

However, the Cubs have had Darwin Barney play shortstop this spring and also have Emilio Bonifacio and Donnie Murphy as infield options as well.

"Right now, it's Friday, and [Castro] went through everything extremely well [Thursday], and I have nine days left," Renteria said. "I've got to set up a schedule for him to participate before we can determine [if he'll be ready]."

Castro said he's had no discomfort doing the infield work and light baseball activities so far, but he has not been on the field for more than a few innings, so his game conditioning is not quite there. The shortstop is coming off a disappointing season in which he batted .245, and he has said he wants to get back to being the two-time National League All-Star who collected 207 hits in 2011.

"He's a guy who we all know physically we have to get in a particular type of shape," Renteria said. "Mentally, if he's in a good state of mind, anybody who has a sense of confidence and focus and determination, you have the ability to do a lot of things. Hopefully that will play into his ability to overcome this little setback that's occurred this spring."

Last spring, Castro strained his left hamstring and only missed two weeks. He's been out nearly three this March.

"I know he wants to play," Renteria said. "It affected him. He hated this setback this spring, obviously. He wants to show everybody and have a comeback-type season. He looks like he's ready to get back out there on the field."

Looking to make team, Rusin impresses vs. White Sox

CHC@CWS: Rusin holds White Sox scoreless over five

GLENDALE, Ariz. -- Chris Rusin has done everything he can to convince the Cubs he's ready for the big leagues. Now, it's up to them.

On Friday, the left-hander gave up two hits over five scoreless innings in a 7-0 win over the White Sox. In his last three outings, Rusin has given up three hits, no runs, no walks and struck out five over 12 innings.

"I was able to pound the zone again with strikes with all my pitches," Rusin said, complimenting the defense as well. "I just need to work on my curveball for strikes and that's what I did today. So far, everything's going as planned."

That doesn't mean he can plan on where he'll be in April just yet. The Cubs do have an opening in the rotation. Jake Arrieta was projected to start, but he's been slowed with shoulder issues. The Cubs could use Carlos Villanueva in that spot until Arrieta is ready.

Is Rusin looking ahead?

"Nah -- it's getting close to the end [of camp]," he said. "I try not to. You've got to figure out where to live and all that, so you think about it a little bit. I'm still even keel and not thinking about too much."

The left-hander ranks second on the Cubs in Cactus League innings pitched this spring, although some, such as Travis Wood, have been staying on track in the Minor Leagues. On Friday, Wood tuned up for the season with six innings against the D-backs' Triple-A team, giving up three runs on seven hits and two walks over six innings, striking out nine.

"I just have to keep doing what I'm doing, that's the only thing I can do," Rusin said. "I have to check the chart tomorrow and hopefully don't get a call into the manager's office. We'll see tomorrow."

Rusin has pitched in the big leagues the last two seasons, but wasn't called up until late in the season after roster moves were made.

Last spring, Rusin compiled a 1.93 ERA over four games, and held batters to a .218 average. But he didn't break with the team.

"My confidence is very high," the lefty said. "I had a great spring last year, too, but this year, to follow it up with another good spring, which is an important time for me, is big. I've just got to keep going, that's all I can say about that."

Cubs manager Rick Renteria knew Rusin would take a low-key approach.

"I don't think [Rusin] goes out there and thinks, 'God, I really need this,'" Renteria said. "I think he just goes out there and pitches. He's got a pretty decent mindset. He lets things take care of themselves."

Baez exits game early with right heel contusion

CHC@CWS: Baez singles before being removed from game

GLENDALE, Ariz. -- Cubs top prospect Javier Baez left Friday's game with a right heel contusion after stepping awkwardly on first base in the sixth inning on an infield single.

With one out in the sixth and the Cubs leading 4-0 against the White Sox, Baez hit a grounder to shortstop Alexei Ramirez. Baez beat the throw, but appeared to slip as he stepped on the bag with his right foot.

Cubs assistant athletic trainer Ed Halbur went out to talk to Baez, who was lifted from the game. The injury was not serious, and Baez will be re-evaluated on Saturday.

Baez entered the game with five home runs, tied with the Blue Jays' Jose Bautistia, the White Sox's Jordan Danks, and the Reds' Chris Heisey for the most in the Majors this spring. Baez also leads the Cubs with 13 hits and 31 total bases. The Cubs infielder finished the day 1-for-3, stranding four runners in his two previous at-bats.

Is there any chance the shortstop will be playing at the big league level this year?

"Anything's possible," Cubs manager Rick Renteria said. "I can't discount any of that. In the immediacy, I think we're as pleased as everybody else is as to how he's shown this spring. I think he had a pretty good showing last spring also. We'll just take it day by day and see how we go."

Extra bases

Junior Lake has been "power shagging" during batting practice, which means he's been asked to go after fly balls as if it's a game situation. On Thursday, the Cubs outfielder robbed a player of a home run with a leaping catch at the wall in left. This is just his second season as an outfielder after spending most of his time at either shortstop or third base.

"He's trying to run scenarios over in his head while he's doing plays in batting practice," Cubs manager Rick Renteria said. "As far as we're concerned, he's improving and working to becoming a better outfielder."

Lake also spent some time in the Cubs' Minor League camp, getting extra at-bats this week, and had two hits, including a RBI single, in a 7-0 win Friday over the White Sox.

• The Cubs entered Friday's game with a team on-base percentage of .298, tied for last in the Majors with the Red Sox. However, Renteria likes what he's seen of the players' approaches at the plate, which has produced long at-bats.

"That mentality and that approach is what we've been trying to implement and I think it's starting to happen," Renteria said. "I think over the long haul, once we get into the season and guys are playing on a regular basis and can maintain that approach, hopefully those results will show up in the numbers."

• Outfielder Casper Wells underwent an MRI on his back and was waiting for results. Wells was 1-for-13 in eight games this spring before he was sidelined.

• Barret Loux, 24, whom the Cubs acquired from the Rangers in the Geovany Soto deal in 2012, underwent Tommy John surgery on his right elbow this week in Chicago. The Cubs had originally acquired Jake Brigham for Soto, but there were concerns about his health. Brighman was returned to the Rangers because of an elbow injury, and Loux was then sent to Chicago to complete the deal. At Triple-A Iowa last season, Loux was 4-6 with a 4.84 ERA in 19 games (16 starts).