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7/7/2013 6:23 P.M. ET

Month after knee surgery, Kratz to start rehab stint

Phillies catcher begins assignment Monday at Triple-A Lehigh Valley

PHILADELPHIA -- Phillies catcher Erik Kratz is ready to go.

He has been on the disabled list since June 9 because of a torn medial meniscus in his left knee. He had surgery to repair the knee a short time later, but he learned Sunday he will begin a rehab assignment Monday with Triple-A Lehigh Valley.

"I'm pretty much doing everything," he said before he got the news.

Kratz, who remains fourth on the team with eight homers, has been hitting, catching and running. He said he feels better than he felt before he injured himself last month running to first base in Milwaukee.

"I'm very surprised," Kratz said. "It's amazing. I know I'm supposed to take my time, but I've passed every test. Eventually, you'll have to play in a game. I feel really close to that."

Left-hander Jeremy Horst, who has been on the DL since June 16 with a sprained left elbow, will continue his rehab with Lehigh Valley. He made his first rehab appearance Saturday with Class A Clearwater.

Howard to have MRI on ailing left knee Monday

PHILADELPHIA -- For about two months, Phillies first baseman Ryan Howard dealt with pain in his left knee. But while taking ground balls during batting practice Saturday, Howard said he really struggled to move laterally, and did not want to push his knee any further.

Howard was originally in the Phils' lineup Saturday, but by the start of the game, the slugger was on the disabled list with inflammation in his left knee.

"It was really hard to move, it just felt stiff," said Howard, who spoke to the media about his DL trip after Sunday's game. "I mean, there's been times where it kind of felt stiff before, but the pain and the stiffness was just too much to where I knew I couldn't go out there and do it. I had to go let them know."

Howard is scheduled for an MRI on Monday. He said he would know more about a course of action once doctors are able to take a look at his knee.

"I guess we'll see what happens tomorrow to get a better understanding of what is going on inside of there, and then address it from there," Howard said. "As far as surgery or any other injections, right now I guess it's too early to tell."

The first baseman initially got an MRI on the knee in mid-May, but after he received a cortisone shot, he continued to play. Howard hit .337 in his first 30 games after the treatment, but had just four hits in his last 31 at-bats before going on the DL.

Howard was held out of the lineup four times on the club's 10-game road trip, but played Friday against the Braves and hit a towering home run -- his 11th of the season. Howard, who is in the second season of a five-year, $125 million contract, is hitting .266 with 43 RBIs in 80 games.

Manager Charlie Manuel also noted that Howard's foot was bothering him. Howard said he has had some "small discomfort" in the bottom of his left foot, but his knee is definitely the main area of concern.

Howard was able to crack a few smiles Sunday, and when he was asked if there's an activity that bothers him the most with the injury, he replied "Yes, doing interviews."

Darin Ruf was recalled from Triple-A Lehigh Valley to replace Howard and is 2-for-4 with a double and two runs in two contests. Meanwhile, Domonic Brown will take over the cleanup role in Howard's absence. The All-Star left fielder hit an RBI triple and a solo homer in a 7-3 win Sunday over Atlanta.

Ruf starts at first base, will get a lot of playing time

PHILADELPHIA -- In a 24-hour span, Darin Ruf went from Triple-A batting practice to having two hits in two Major League appearances this season under his belt.

Ruf was recalled from Triple-A Lehigh Valley by the Phillies on Saturday to replace Ryan Howard on the 25-man roster. Howard's sore left knee forced him to the disabled list.

Lehigh Valley was in Scranton on Saturday, and Ruf had to make the drive of two hours and change from Scranton to Citizens Bank Park by himself. The announcement of Howard's DL stint came close to game time, so Ruf had a late jump and said he did not arrive at the ballpark until the fifth inning.

"Our trainer came up and told me to get to Philly as soon as possible," Ruf said. "Derek Jeter was playing [Saturday] in Scranton, so it was a little tough getting a car in there, but I finally made it."

Ruf entered Saturday night's 13-4 loss to the Baves in the eighth and was 1-for-2 with a single. He followed that up with a 1-for-2 showing in Sunday's 7-3 win. He doubled, walked and scored twice.

The 26-year-old started at first base and hit seventh in the order. Though he came out of the game in the seventh, manager Charlie Manuel was pleased with the way Ruf played in his hectic weekend. Manuel said he expects Ruf to see plenty of action at first base with Howard injured.

"I think he's going to get a lot of playing time there," Manuel said. "More than likely, yeah [he's going to be the first baseman with Howard out]. That's why we called him out."

Ruf also appeared in 12 games for the Phillies after a September callup last season. He hit .333 (11-for-33) with two homers in his short spell.

Some fans may have hoped to see Ruf at Citizens Bank Park earlier than the first week of July, as the first baseman/left fielder battled for a spot on the roster during Spring Training. Ruf hit .246 with two homers and six RBIs and was sent to Triple-A.

"I just put too much pressure on myself or something or other," Ruf said of his spring. "I just settled in as time went on. It was still early, starting a couple of weeks earlier than I was used to, it took me a little bit longer to get back into the swing of things. I'm happy with the way I finished and the progress I made."

Ruf was called up last season after hitting 38 homers by the end of August for Double-A Reading, but his numbers were not as impressive this season. He's hit .266 with seven homers in 82 games. The 6-foot-3 right-hander did deal with a thumb injury, but said he is 100 percent healthy.

Worth noting

• Entering Sunday, Phillies starters had just one win in their last 16 weekend (Saturday or Sunday) starts. The team's starters were 1-10 in that stretch.

• The Phillies surrendered 10 or more runs for the eighth time this season Saturday. That mark ties them with the Giants for the most in the National League, and only the Mariners and the Astros have allowed a team to score double-digit runs more often.

Todd Zolecki is a reporter for MLB.com. Stephen Pianovich is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.