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6/13/2014 12:08 A.M. ET

Bonifacio injures rib cage, status in question

PITTSBURGH -- Cubs leadoff batter Emilio Bonifacio may be headed to the disabled list after suffering a right rib cage injury on Thursday.

The team did not expect to know the extent of the injury until Bonifacio is examined in Chicago on Friday. Bonifacio was not available after Thursday's game, a 4-0 loss to the Pirates. The Cubs were headed to Philadelphia for a three-game series starting on Friday.

On the second pitch of the game, Bonifacio grounded out to short, but he never left the batter's box. As he swung, he fell to the ground, grimacing in pain. Head athletic trainer PJ Mainville had to support Bonifacio as he limped off the field.

Cubs manager Rick Renteria said he did not get a chance to talk to Bonifacio before he left, and did not know the severity of the injury.

Junior Lake switched from left to center to fill in for Bonifacio, and Chris Coghlan came off the bench to play left. The Cubs have been carrying an extra pitcher, and playing shorthanded as far as position players go.

Bonifacio is 1-for-11 in his last four games, but he's been the most versatile player on the Cubs, starting 36 games in center, 19 at second, and one at third. He batted .337 in the first month of the season, but has cooled off since, hitting .222 in 10 games this month.

Outfielder Ryan Sweeney, who has been on the disabled list since May 3 with a right hamstring strain, was scheduled to make a rehab start Thursday for Class A Kane County but was scratched from the Cougars' lineup. He could be headed to Philadelphia to join the big league team. Sweeney batted .200 in 20 games before he was injured.

An unlikely cleanup hitter, Castro settling into spot

PITTSBURGH -- Last season, Cubs shortstop Starlin Castro batted everywhere but fourth in the lineup, including one game when he was hitting ninth. This year, although Castro has a few games at other spots, he has settled into the No. 4 spot.

But manager Rick Renteria said Castro isn't a No. 4 hitter.

"He isn't," Renteria said Thursday. "But he's doing well. All things being equal and looking at how they're performing, I'll leave him where he's at. For us, for our club, he's the one who seems to fit there the best.

"He's not bothered by it," Renteria said of Castro, who was batting .272 in the No. 4 spot entering Thursday's finale vs. the Pirates. "He doesn't think about it in any way shape or form of being the 'fourth hitter.' He just sees himself as being there to hit -- whether he's in the fourth slot or the second. I don't think he thinks about it."

Castro wasn't happy bouncing around, and has said he likes being in one spot in the lineup. It's not that he changes his approach physically.

"It doesn't hurt if you have the ability to leave them in a particular slot, to leave them there," Renteria said. "It's more mental than it is anything. If that gives a hitter the edge, you try to keep that."

Valbuena in sustained groove with the lumber

PITTSBURGH -- Luis Valbuena is on a hot streak, and Cubs coach Jose Castro isn't surprised.

"I remember in 2008 with Seattle when he used the opposite field was when his swing really ticked, and that's what he's been doing," said Castro, who was the Mariners' Minor League hitting coordinator that year, and promoted to the big league staff as hitting coach.

"[Valbuena] can turn on the ball," Castro said. "It's more using the big part of the field, and that's what he's been doing. His pitch recognition is really good, and therefore his plate discipline and strike-zone awareness more than anything is really good."

Entering Thursday's game, Valbuena was batting .384 (28-for-73) with 10 doubles, two homers and eight RBIs in his last 22 games. The .384 average was tops in the National League in that stretch.

Castro has seen Valbuena in-season and in the winter playing in Venezuela. For the last four years, Castro has coached or managed winter ball, and Valbuena has played on his team.

"He knows the strike zone, and very rarely do you see him chase," Castro said. "When he does, you say, 'That's not him.' He's so consistent and has a good at-bat, and it seems like he's always 3-2 [in the count]."

Valbuena has batted fifth most of the season, and manager Rick Renteria likes the left-handed hitter there.

"He's a guy who you've seen put together really good at-bats, and it doesn't matter if it's a righty or lefty [pitching]," Renteria said. "It seems to suit him well. If he was in the two-hole, he'd probably do the same."

Castro isn't surprised at the success Valbuena is having.

"I saw him in 2008 his first time in the big leagues, and it's just staying within yourself and knowing what's best for him," Castro said.

Villanueva not fazed by hostile environments

PITTSBURGH -- The Cubs have had trouble on the road this season, and pitcher Carlos Villanueva didn't blame the hotels or the travel or having to eat in restaurants as the problem.

"When you're home, you just feel comfortable," Villanueva said. "You have your crowd behind you."

One of the toughest places to play? St. Louis, Villanueva said.

"You always feel the pressure of their crowd," he said. "Of all the places I've played -- I don't know if it's the red seats and even if they're empty, they feel like they're packed -- but the best baseball atmosphere is in St. Louis. They don't boo anybody. They know baseball, they cheer for the opposing team if they do something well.

"You always feel [the Cardinals] have a chance," Villanueva said. "In the psyche of the players, it helps. You get a 1-0, 2-0 count, and everybody gets riled up. We have young relievers, and they say, 'Oh, man, what's going on?' That's when you have to step out. You've got a four-run lead, three-run lead, you have to tune out the people. If you're home and you have the excitement, you want to do it for the people."

The Cubs are 15-14 at Wrigley Field, and were 11-23 on the road prior to Thursday's game against the Pirates. On Friday, they'll open a three-game series in Philadelphia, which is notorious for being tough on visiting teams.

"The only time I was fortunate enough to go to the playoffs was against the Phillies, and that was crazy," Villanueva said of the 2008 National League Division Series. "I am lucky, because I'm thick-skinned and it's never bothered me. I take it in stride, and I smile at the fans. But they're brutal -- they'll talk about your mom, your sisters."

Villanueva does his own yelling at players when he's watching winter league games in the Dominican. But he only yells at players he knows, and they take it well.

"They can be tough [in Philadelphia]," Villanueva said. "It just depends on the personality you have. If you're a guy who gets riled up by it, it'll affect you."

How does he handle it?

"You smile every day," Villanueva said.

Extra bases

• The Cubs signed Yorvit Torrealba to a Minor League deal on Thursday, and the veteran catcher was to report to the team's complex in Mesa, Ariz.

A career .256 hitter, Torrealba, 35, had signed with the Angels in January, but was released on March 23. He has played for the Rockies, Giants, Rangers, Padres, Mariners, Brewers and Blue Jays. Last season, he appeared in 61 games with the Rockies, batting .240 with eight doubles and 16 RBIs.

There was no timetable for how long Torrealba will work out in Mesa.

• The Cubs will continue to carry 13 pitchers, and so far, Renteria said he hasn't missed having an extra player on the bench. Most teams carry 12 pitchers.

"It's actually possibly helped us to have the guys we have, so we can gain some length," Renteria said. "It also allows us to give guys some days off with the usage in certain instances."

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.