CLEVELAND -- Left-hander Dallas Braden will have to wait until after the All-Star break to notch the win he's been looking for since tossing a perfect game on May 9.

A's manager Bob Geren said on Friday that Braden will miss his scheduled start on Saturday, due to elbow tightness that kept him from taking the mound in Baltimore on Tuesday.

In his stead, right-hander Clayton Mortensen will be promoted from Triple-A Sacramento to start against the host Indians.

Braden, battling a dose of elbow tendinitis, came out of a 25-plus pitch bullpen session on Thursday feeling well, but Geren said the club wants to give him "as much time as he needs to get himself feeling better." Thus, to make room for Mortensen on the roster, Braden is likely to be placed on the disabled list on Saturday.

Oakland can afford to skip Braden's next turn in the rotation on July 8, when the club has a scheduled off-day. Then, with the All-Star break awaiting just four days later, the southpaw can potentially rest until July 20 and jump into the back end of the rotation.

"We'll look at the rotation," Geren said. "We'll consider who needs the most time out."

Mortensen was one of two Sacramento players -- the other Josh Donaldson -- recently named to the Pacific Coast League All-Star team. The 25-year-old righty, owner of a 10-2 record and 3.58 ERA this season, was held out of his scheduled start for the River Cats on Thursday in the event Braden was unable to go.

In 98 innings pitched for Sacramento this year, Mortensen has compiled 77 strikeouts, good for third in the PCL. Meanwhile, he's walked just 31. He made seven appearances -- six of them starts -- for the A's last year, struggling with a 2-4 record and 7.63 ERA.

However, the improvements he's made since then, as noted by Geren, show in more than just his current numbers.

"We'd like to see a performance similar to what he's been doing," the skipper said. "He's been throwing strikes and throwing his sinker for strikes. That's his key pitch, so that's what you want to see."

A's bring Bonser, Lyman on board

CLEVELAND -- The A's on Friday signed free agent right-hander Boof Bonser to a Minor League deal and also claimed right-hander Jeff Lyman off waivers from Atlanta.

Bonser, just days removed from his release by the Red Sox, will immediately report to Triple-A Sacramento, where Oakland assistant general manager David Forst said the club hopes to stretch him into a starter.

The 28-year-old has spent the majority of the season on the disabled list. He allowed four runs in just two appearances with Boston this year.

Lyman, meanwhile, was optioned to Double-A Midland and will shed his reliever role and transform into a starter, which is how the A's envisioned him upon first seeing him in 2005, when he was drafted by the Braves in the second round out of Monte Vista High School in Danville, Calif. -- located less than 30 minutes from Oakland.

"He's a guy we liked a lot out of the Draft," Forst said on Friday. "We saw him in our backyard when he was in high school. He has a good arm and is still really young, despite how much time he's spent in the Minors."

The 23-year-old Lyman began the season at Triple-A Gwinnett and was 0-0 with a 4.72 ERA in 21 relief appearances before being transferred to Double-A Mississippi on June 30. He made just one appearance there, allowing one run on two hits in one inning on Thursday.

"We'd like to develop him as a starter," said Forst, who noted that starting pitching is an area which the entire organization would like to improve as a whole. "We think he can be stretched out as a starter and help us out that way."

Oakland signs three Venezuelans

CLEVELAND -- A trio of Venezuelan players were officially welcomed into the A's fold on Friday, as Oakland agreed to terms with three international free agents.

Renato Nuñez, a 16-year-old right-handed hitting third baseman, along with 17-year-old lefty Anderson Mata and 16-year-old southpaw Jose Torres, will report to Oakland's complex in the Dominican Republic following physicals and approval of their contracts.

According to A's coordinator of international operations Dan Kantrovitz, Nuñez not only represents a player the club has eyed for a couple of years but also one of the "top bats" in all of Latin America.

"As we got to know him on and off the field," Kantrovitz said, "we realized what a good head he has on his shoulders. He's smart. And we think very highly of his bat profile. He was No. 1 on a few of our scouts' prep list."

Torres and Mata, meanwhile, are pitchers the A's are attracted to for different reasons. Torres, said Kantrovitz, owns a curveball "you don't see from many kids his age." Then there's Mata, who he sees as something of a "sleeper."

"He has three pitches he can throw for strikes. His current arsenal -- fastball, curveball, changeup -- is already very developed. He's someone we've been very impressed with because of his pitchability, as opposed to just his arm strength projection, which is already pretty good."

Worth noting

Daric Barton, who left Thursday's game with injuries to both legs, was inserted into Friday's starting lineup, where Adam Rosales was initially penciled in at first base, at the last minute. ... Conor Jackson was held out of the lineup for the second straight day due to right hamstring soreness. Manager Bob Geren said the outfielder is still day-to-day, but "it's going to be a few days." Jackson spent some time on the disabled list in April with Arizona as a result of a right hamstring strain. ... The A's on Friday agreed to terms with their 39th-round Draft selection, Clemson catcher John Nester.