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6/29/2013 4:51 P.M. ET

Casilla heads out for first rehab appearance

DENVER -- Santiago Casilla packed his bags in the Giants clubhouse before a game against the Rockies on Saturday as he prepared for his first rehab outing Sunday, where he will start the game and pitch one inning.

Casilla's start with Class A San Jose comes against the Stockton Ports at home, and he will toss about 20 pitches. He's expected to make several rehab appearances before he rejoins the Giants, and Casilla said the exact number will be based on how he feels after each appearance.

Casilla has been out since May 20 after having surgery to remove a cyst from his right knee. But a bullpen session against live batters at Coors Field on Friday went smoothly, and Giants manager Bruce Bochy said he could be back in a Giants uniform in the next week.

"We'll evaluate him after each inning, see where he's at, how he feels," Bochy said. "He could be ready as soon as the next homestand if all goes well."

The right-handed reliever served as a reliable bullpen arm before the injury with a 1.89 ERA in 21 appearances (19 innings).

Role undetermined, Gaudin expected to return quickly

DENVER -- San Francisco's pitching staff will get another boost soon as Giants manager Bruce Bochy said he's confident Chad Gaudin will be back next weekend.

Gaudin threw a bullpen session at Coors Field on Saturday, and Bochy said he isn't sure if the righty will join the starting rotation or work from the bullpen.

Gaudin took a line drive off his elbow June 20 and though X-rays were negative, he was eventually placed on the 15-day disabled list. His last four appearances were starts, but he spent the first two months of the season as a reliever.

"We'll see where we're at, where we think we get the most value from him," Bochy said. "He's so valuable in both the spots."

Since Gaudin went down, rookie Mike Kickham has filled his spot in the rotation. Kickham has struggled in the first two big league starts of his career, allowing six runs (five earned) and eight hits in 5 1/3 innings in a loss to the Dodgers on Tuesday. His other start came May 28, when he surrendered four runs to the A's in just 2 1/3 innings.

"With [Kickham], we're just going to go one start at a time, see how he handles it," Bochy said. "If we have to make adjustments, we will. We always have the option that when Gaudin comes back, put Kickham in the 'pen, start Gaudin or put Gaudin in [the bullpen]."

Gaudin carried a 3.38 ERA in his four starts, and Kickham's start against Cincinnati on Monday may help Bochy decide who ends up in the bullpen. Bochy said he does think Kickham has the arsenal to be a long-inning reliever.

"I like a lefty long man and I think he's got the equipment to do that. ... But right now we need him starting."

Worth noting

• With Rockies lefty Jorge De La Rosa starting, Bochy decided to sit first baseman Brandon Belt and slide usual catcher Buster Posey to first base. Posey has started three of the last eight games at first base and has eight starts there this year.

• Bochy said Saturday starter Matt Cain has pitched better than his ERA indicates. Cain has allowed three earned runs or fewer over his last four starts despite his early season struggles. The righty had a 6.49 ERA in April but has shown promising improvement with a 3.58 mark in June.

Ian McCue is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.