CHICAGO -- Cubs catcher Geovany Soto was scratched from Thursday's lineup against the Phillies because of inflammation in his left knee and was scheduled to undergo an MRI exam on Friday. His status was day to day.

Welington Castillo, who was batting .150, replaced Soto in the Cubs lineup in the series finale against the Phillies and was 2-for-4, hitting a solo homer and three-run double for a career-high four RBIs.

"He came up in batting practice a little sore," Cubs manager Dale Sveum said Thursday of Soto. "He started taking some swings and just got really sore so we'll get that evaluated [Friday] by the doctor. He's still available for emergency situations. He's not down and out, there's just some fluid and stuff."

Soto said he had some discomfort when he woke up Thursday. He was hitting .161 with three home runs and six RBIs this season, and has started 27 of the Cubs' 37 games. Although his batting average is low, he's shown some improvement. He hit .127 in April and was batting .211 in May.

Parker impresses in big league debut

CHICAGO -- Right-hander Blake Parker impressed Cubs manager Dale Sveum this spring, and now he'll get a chance to do so in the big leagues.

"I liked him a lot in Spring Training," Sveum said Thursday. "He's got an above-average slider, and that's one thing we need right now is somebody who can go through right-handers with a slider. He's got velocity. He's a guy who has done a nice job and you have to start rewarding guys who've done a nice job."

Parker, 26, was rewarded when he was called up from Triple-A Iowa to the Cubs on Thursday. He made his Major League debut in the seventh inning and struck out the first batter he faced, the Phillies' Ty Wigginton, then gave up an infield hit to Hector Luna. Parker then got Freddy Galvis to hit into a double play to end the inning.

So far, so good. But in the eighth, the Phillies had runners at second and third with two outs and Parker fielded Hunter Pence's swinging bunt, then overthrew first for an error. Two runs scored.

"If there's one thing I pride myself on, it's [pitchers' fielding practice]," said Parker, upset about the errant throw.

The good news is that he wasn't intimidated about pitching in a big league ballpark. He had about nine family members and friends who flew to the game at Wrigley Field.

"I felt right at home," Parker said.

Left-hander Scott Maine was optioned to Iowa to make room.

"I've been waiting a very long time, but it makes it so much more rewarding and worthwhile when you get that call," Parker said. "It's almost just sinking in."

A 16th-round pick in 2006, Parker was 1-0 with five saves in five opportunities in 13 games at Iowa, giving up three earned runs on nine hits over 13 innings. He held hitters to a .200 average.

The Cubs' bullpen could use some help. The relievers have the worst record in the National League at 5-11, and they rank 26th in the Majors with a 4.76 ERA. Carlos Marmol and Lendy Castillo, who were both in the 'pen at the start of the season, are now on the disabled list, and rookie Rafael Dolis has taken over as closer.

"It's a bullpen right now that's in a 'what's going to happen tonight'-type thing with who are you going to use in this situation," Sveum said. "Unfortunately, we're putting some guys in situations where they've never had to pitch before, which is unfortunate for them, but they've done a good enough job where they can get by."

Parker has a little help in the inspiration department. He wears his grandfather's ID tags. Jack Parker served in the Air Force and saw action in World War II and Korea. He needed the support after a down season in 2010. He's bounced back nicely.

"After a down year, you don't let it get you down," Parker said. "Baseball is a tough game and a game of failure, and recovering from that. I've never given up, and you work hard to get to your goal."

Iowa manager Dave Bialas called the right-hander around midnight Wednesday with the news.

"I wasn't expecting it at all," Parker said. "It was a weird number, a Florida number from the manager, and I recognized his voice immediately, but I didn't think that's what he was calling for."

Sveum said he'll stick with Dolis as the closer, but if the Cubs need Parker in late inning situations, he's ready.

"That's a position I've always liked to be in, coming in with the game on the line and a little more pressure filled situation," Parker said. "I've always kind of thrived on that."

Samardzija pumped for Windy City Series

CHICAGO -- Jeff Samardzija couldn't hide his excitement about pitching on Friday against the White Sox at Wrigley Field.

"I'm just excited -- I'm really excited, actually," Samardzija said Thursday. "I love pitching here in Chicago, and especially in front of both sets of fans. The place should be rocking, and it should be fun."

The Cubs open Interleague Play on Friday against their crosstown rivals, beginning the home-and-road six-game series at Wrigley. Samardzija will face Philip Humber in Game 1. The series is important to fans as far as bragging rights are concerned in the city. And the players?

"There are certain games on the calendar you look at and circle, and not for any other reason than you know it'll be exciting and there will be a buzz around the area and around Wrigley," Samardzija said. "I'm looking forward to pitching down there -- that's like pitching in my backyard at Comiskey, it's like 20 minutes from my house."

Of course, the White Sox home park now is known as U.S. Cellular Field, not Comiskey Park. But for Samardzija, who grew up in Valparaiso, Ind., it's close to his home.

Samardzija has been on a good roll. The Cubs are 6-1 in his seven starts, and he's compiled a 2.89 ERA in his first full season as a starter.

"I think [the season] is just going in the right direction with how I feel and how my pitches are coming out," he said. "Obviously, you need to get better every time out and I think I've been trying to improve and seeing how teams approach me at the plate. ... I was watching the White Sox, and they have some big bats in there and some guys I definitely have to be careful with, especially here, where it will be a nice day tomorrow and the wind blowing out a little bit."

Samardzija did listen to White Sox games on TV and enjoyed broadcaster Hawk Harrelson's unique calls.

"I always liked the ones where he didn't talk for about an inning and a half, and all of a sudden, he'd be, 'OK, the 2-2,'" Samardzija said. "Where did the other 15 pitches go?

"They're fun to watch and fun to listen to. You can always get a good nap in during a Sox game."

Let the crosstown series begin.

Garza turns attention to bunt defense

CHICAGO -- Matt Garza's defensive play can be an adventure sometimes, but on Thursday he was participating in the Cubs' bunting drills and working on his fielding.

"That's all it is is getting my athletic legs back under me," said Garza, who bounced his throws to first base after fielding two of Juan Pierre's bunts on Wednesday.

If opposing teams want to continue to bunt against the Cubs right-hander, he's ready.

"If that's the game plan to go against me, we'll have a lot of fun and a lot of quick games," Garza said. "I'm just trying to get everything better, get everything right, hitting, bunting, everything. I want to be an all-around ballplayer. I don't want to be stuck."

He said he became a one dimensional pitcher in the American League, focusing only on pitching.

"People didn't bunt as much," he said of his days with the Twins and Rays. "It was the AL East, it was, 'See how far they hit the ball,' and as a pitcher, your job was see how far they couldn't hit the ball."

Cubs manager Dale Sveum was pleased at Thursday's early work.

"He did a great job," Sveum said. "It was awesome."

Extra bases

• The Cubs are batting .255 in May after hitting .237 in April, and in the last 20 games since April 24, they have outhomered their opponents, 20-13.

"The guys are doing OK, but we have to be a lot more consistent on a daily basis," Sveum said.

Chicago hit .277 in a five-game trip to Milwaukee and St. Louis, but was held to three hits Wednesday against Philadelphia.

• Blake DeWitt has accepted an assignment to Triple-A Iowa. The infielder was designated for assignment for the second time this year on May 6, cleared waivers and was outrighted to the Minor League team. DeWitt was batting .138 in 18 games.