UPDATE: Chase Headley has been diagnosed with a small fracture in his left thumb and could miss the first month of the season, reports Corey Brock of MLB.com.
The exact timing of Headley's return is still up in the air, but a four-week timetable is thought to be "optimistic," according to Bill Center of the San Diego Union-Tribune.
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Headley sustained his thumb injury -- initially termed a jammed thumb -- while attempting to break up a double play during yesterday's spring training contest against the Los Angeles Angels. The third baseman singled in the first inning and went on to jam his thumb against second base when he slid into the bag.
After the game, manager Bud Black told reporters that Headley would undergo "X-rays and maybe some other scans" to help diagnose the severity of the injury.
Headley was San Diego's top offensive player last season. The 28-year-old hit .286/.376/.498 with 31 doubles and 31 home runs over 699 plate appearances last season. He owns a career batting line of .273/.351/.418 over parts of six seasons in the majors.
If Headley is forced to start the regular season on the disabled list, Brock expects the Padres to turn to either Logan Forsythe or top prospect Jedd Gyorko. Forsythe is close to returning to exhibition contests, but he's been sidelined with plantar fasciitis since March 7.