SEATTLE -- A's right-hander Trevor Cahill, who revealed a left scapula stress reaction just two days before Opening Day, was cleared to throw again after visiting orthopedist Lewis Yocum in Anaheim on Sunday.

Cahill began the season on the disabled list next to five other A's players, including fellow pitchers Michael Wuertz and Joey Devine. He said the neck pain began at the end of last season and resurfaced after his Minor League start on March 29.

The 22-year-old pitcher made 32 starts as a rookie last season and was expected to have the edge for the fifth rotation spot entering camp. However, his injury -- combined with a strong showing from Gio Gonzalez -- led the A's to go with the left-hander.

Manager Bob Geren noted that Cahill is seemingly only a week behind other pitchers. But where the righty fits into the A's picture after fully recovering is unknown. There is no timetable for his return.

Sore hamstring sidelines A's Ellis

SEATTLE -- Less than 24 hours after tallying his fourth multihit game of the season, Mark Ellis was sidelined with a sore left hamstring and deemed day-to-day.

According to manager Bob Geren, the A's second baseman should not be out longer than two days.

"We're not really looking at it as anything more than a day-to-day thing," Geren said as the A's prepared to take on the host Mariners for the first of a three-game set. "It's more precaution."

Ellis, who was slotted in the designated hitter's spot Sunday afternoon against the Angels, suffered the injury in the eighth inning while running to first on an infield ground ball that resulted in a Brandon Wood throwing error. He stayed in the game and reached base in the ninth on a single to left field but was immediately relieved by pinch-runner Travis Buck.

The 32-year-old Ellis, who experienced hamstring tightness for a handful of days in Spring Training, entered Monday with the club's second-highest batting average (.345) next to Daric Barton, who is hitting .381.

Adam Rosales will fill second-base duties while Ellis recovers, and he'll carry with him an impressive starting debut that saw him go 2-for-3 with a home run and go-ahead single on Sunday.

Gross gets first start for A's

SEATTLE -- For the second consecutive day, A's manager Bob Geren pulled from his bench to fill in his outfield Monday.

Gabe Gross received his first start in left field after collecting just two at-bats in Oakland's previous seven games. He garnered his first hit and RBI of the season as a pinch-hitter in Sunday's contest against the Angels, snapping a career-long 0-for-19 streak dating to last year.

Meanwhile, Opening Day left fielder Travis Buck got his second day off Monday after starting each of the club's first six games -- a span in which he went 4-for-21 (.190), bringing to mind his career April average of .198.

Sunday starter Eric Patterson, who went 0-for-3 while playing left field, is expected to share backup outfield duties with Gross throughout the season. Gross was acquired late in the offseason as a free agent after compiling a .227 average with six home runs in 115 games with Tampa Bay last year.

Worth noting

SEATTLE -- Eric Chavez was given his second straight day off Monday, and manager Bob Geren noted that the Mariners' offering of left-handed starter Ryan Rowland-Smith eased his decision to sit Chavez, who will be given regular rest often. ... Geren on Monday mentioned that right-hander Michael Wuertz (shoulder) felt fine a day after throwing a 28-pitch bullpen session. Wuertz is likely to toss one more bullpen session before making a Minor League rehab appearance. ... Cliff Pennington hit his second homer on Monday after tallying four through 60 games in Oakland last year. ... Daric Barton has reached base safely via hit or walk in all eight games.