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6/11/2014 7:28 P.M. ET

Scuffling Olt out of Cubs' lineup vs. Bucs

PITTSBURGH -- Hitless over his last seven games entering Wednesday, Cubs third baseman Mike Olt did not start vs. the Pirates.

"We have to let it play itself out and make sure we do everything we can to allow him to do whatever he needs to do to put himself in a position where he's feeling good about what he's doing," manager Rick Renteria said. "By the same token, hopefully the matchups we end up giving him give him a chance to go and get himself back on track."

Olt still leads all National League rookies with nine home runs and 24 RBIs. But he's batting .151 and riding an 0-for-18 slump.

On the other end of the stat sheet is Luis Valbuena, who hit a two-run double on Tuesday, and was batting .362 with nine doubles, two homers and eight RBIs in his last 21 games entering Wednesday. The .362 average is second best in the National League in that stretch.

"He's a guy who has balanced out our whole lineup," Renteria said. "Whether we've used him at second or third, he's been kind of a solidifying force for a lot of the infield."

The Cubs have matched up Olt primarily against left-handers, and he's made 35 starts at third, while Valbuena has started 26 games at third and 14 games at second.

Rehabbing Castillo participating in baseball activities

PITTSBURGH -- Welington Castillo, on the disabled list with rib cage inflammation, is doing baseball activities in Mesa, Ariz. The catcher has so far had no setbacks, manager Rick Renteria said.

Castillo took 25-30 dry swings, 15-20 swings off a batting tee and did some running, Renteria said Wednesday.

The Cubs have missed Castillo's bat, as well as his play calling. Chicago's catchers are batting a combined .206, and Castillo was hitting .242 with five home runs and 21 RBIs over 43 games before being sidelined.

Veteran Eli Whiteside was called up from Triple-A Iowa when Castillo was injured, and he was pressed into duty after John Baker bruised his vocal cords when he was hit by a foul ball in his throat. Whiteside was hitless in 12 at-bats entering Wednesday. Baker, who entered Wednesday batting .154, got the start against the Pirates.

"Whitey and Baker are both experienced Major League catchers," Renteria said. "It helps in depth when you have someone like Whitey, who has been with us since [Spring Training]. You know how he is as a receiver. He was part of a World Series champion club when he was with the Giants."

Cubs extend affliation with Double-A Tennessee

PITTSBURGH -- The Cubs and Double-A Tennessee have announced a four-year player development contract extension which will keep the affiliate in Kodak, Tenn., through 2018.

"Our front office has enjoyed our relationship with the Smokies, and the players who have come through Tennessee have spoken very highly of the Smokies and their fans," said Jason McLeod, Cubs senior vice president, scouting and player development, in a statement.

Since beginning their affiliation with the Cubs in 2007, the Smokies have participated in postseason play in five of seven seasons, and they have advanced to the Southern League Championship Series three times. Tennessee has posted a 553-485 record (.533) as of June 10, with six of seven completed seasons ending with a winning record. The .533 winning percentage as a Cubs affiliate is the best in Smokies history.

"There's no question the talent that has come through Kodak recently has been some of the best in baseball, and it's an amazing opportunity for fans to see the stars of tomorrow pass through here," Smokies general manager Brian Cox said. "The impact the players and coaches have made in East Tennessee has been tremendous, and the future is clearly bright for both the Chicago Cubs and Tennessee Smokies."

In total, 35 Smokies have made their Major League debuts with the Cubs, including Jeff Samardzija, Starlin Castro, Darwin Barney and Welington Castillo.

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.