CHICAGO -- Cubs catcher Welington Castillo may have undergone the biggest transformation this season.

Castillo, who has taken over most of the catching duties since Geovany Soto was dealt to the Rangers at the Trade Deadline, was like "a deer in the headlights" in Spring Training, Cubs manager Dale Sveum said Monday. Castillo wasn't that sure of himself even two months ago, Sveum said.

"What he's done in the last six months has been the most impressive of anybody, and he's the most improved guy I've seen this season," Sveum said.

Castillo, 25, has worked with pitching coach Chris Bosio and coach Mike Borzello on each day's game plan, and is counted on to handle the pitch calling. Sveum said the transformation is a combination of more playing time, Soto's departure, and the realization that Castillo has a chance to be an everyday big league catcher.

"It's not that 'yes' man anymore," Sveum said of the young catcher. "He'll actually have input on situations. There are definitely guys who are starting to step up and going into Spring Training, it'll be a very different atmosphere than going into it this past spring."

Castillo took it as a challenge.

"I want to be a leader one day, and why not start now?" Castillo said. "They're giving me an opportunity to be an everyday catcher and I think I have to take advantage of that and start doing that now. I feel really good and appreciate the confidence they have in me."

Castillo opened the season at Triple-A Iowa. He played nine games for the Cubs in the first half of the season, and has been behind the plate for 41 games in the second half. He likes the added responsibility the coaches and Sveum have given him, and the preparation involved for that day's game. He's doing his homework.

"When you're behind the plate, you call one pitch, and [the pitchers] know what you're doing," Castillo said. "I think that's helped me, working with Borzello and going over the scouting reports. I'll explain my ideas and they'll explain their ideas, and we get to one point where we know each other and trust each other, too."

Camp, Valbuena prove to be season's big surprises

CHICAGO -- Shawn Camp was released by the Mariners on March 21, and signed a Minor League contract with the Cubs five days later. The right-hander has appeared in a career-high 78 games for the Cubs.

Luis Valbuena was claimed off waivers on April 4, spent most of the season at Triple-A Iowa, and will finish with more starts at third base than Ian Stewart, who had been projected as the Cubs' everyday third baseman.

Cubs manager Dale Sveum tabbed Camp and Valbuena as two of the biggest surprises this season as well as veteran Alfonso Soriano, who has set a career-high in RBIs.

"Soriano has been the biggest every single day, all season long surprise, defensively and offensively," Sveum said. "The person he is, the work ethic and everything has been awesome for a new manager to come in and see what he brings to the table.

"Some of these key pickups right at the end of Spring Training have kept us afloat," Sveum said of Valbuena and Camp. "Those kind of guys have helped us out tremendously or this would have been an even tougher season."

Extra bases

• Starlin Castro won't be getting a day off with three games remaining. On Monday, Castro tied the single-season franchise mark of 160 games played at shortstop, set by Ivan DeJesus in both 1978 and 1979.

Monday's game also was Castro's 159th start at shortstop this year, surpassing the single-season franchise mark of 158 starts set by DeJesus (1978) and Don Kessinger (1968). Castro will try to become the first player in franchise history to play in all 162 games at shortstop.

"At this point now, you get your rest during the winter," Cubs manager Dale Sveum said. "At this point, there's no reason to rest anybody for any reason. We still have a goal to get to, too."

The Cubs' goal is to avoid 100 losses. Castro's is to play 162 games. He could be the first Cubs infielder to make at least 161 starts at a single position since Bill Buckner at first base in 1982. The last Cubs infielder to appear in all 162 games was Ron Santo in 1968.

• Pitcher Nick Struck and infielder Logan Watkins were honored before Monday's game as the Cubs' Minor League Pitcher and Player of the Year. Struck was 14-10 with a 3.18 ERA in 28 games (26 starts) for Double-A Tennessee. He struck out 123 and walked 44 over 155 2/3 innings. Watkins batted .281 with nine home runs, 20 doubles, 11 triples for Tennessee.