1st or 2nd Line MBC (Metastatic Breast Cancer) With Previous Avastin (Bevacizumab) Therapy

Inclusion Criteria: * Histologically or cytologically confirmed adenocarcinoma of the breast. * Measurable or evaluable locally advanced or metastatic disease. * Age ≥18 years. * Disease progression during or after treatment with a bevacizumab-containing regimen in the adjuvant or first-line metastatic setting. * Patients must have discontinued chemotherapy at least 3 weeks prior to randomization. * No more than one prior chemotherapy regimen for locally advanced or metastatic disease. * Prior hormonal therapy allowed provided it has been discontinued prior to randomization. * Prior radiation therapy is allowed but must be completed at least 3 weeks prior to randomization. Previously radiated area(s) must not be the only site of disease. * ECOG Performance Status of 0 or 1. * Adequate bone marrow, liver, and renal function * Women of childbearing potential must have a negative serum pregnancy test performed within 7 days prior to randomization, and must agree to use adequate contraception prior to study entry, for the duration of study participation and 28 days after the last study drug dosing. * Patients must be able and willing to sign a written informed consent. * Patients must be able to swallow and retain oral medication. Exclusion Criteria: * Patients with breast cancer over-expressing human epidermal growth factor receptor 2 (HER-2) (gene amplification by FISH or 3+ over-expression by immunohistochemistry). Patients with unknown HER-2 status are not eligible. * Patients with active brain metastases. * Major surgery, open biopsy, or significant traumatic injury within 4 weeks of randomization. * Prior use of gemcitabine/capecitabine or sorafenib. * Evidence or history of bleeding diathesis or coagulopathy. * Serious, non-healing wound, ulcer, or bone fracture. * Substance abuse, or medical, psychological, or social condition that may interfere with the patient's participation in the study or evaluation of the study results. * Use of cytochrome P450 enzyme-inducing anti-epileptic drugs is not allowed. * Clinically significant cardiac disease * Uncontrolled hypertension * Thrombolic, embolic, venous, or arterial events such as a cerebrovascular accident including transient ischemic attacks within the past 6 months. * Pulmonary hemorrhage/bleeding event \> NCI-CTCAE Grade 2 within 4 weeks of randomization. * Any other hemorrhage/bleeding event ≥ NCI-CTCAE Grade 3 within 4 weeks of randomization. * Active clinically serious infection \> NCI-CTCAE Grade 2. * Known HIV infection or chronic hepatitis B or C (the safety and effectiveness of sorafenib in this patient population have not been studied). * Previous or concurrent cancer that is distinct in primary site or histology from breast cancer EXCEPT cervical cancer in-situ, treated basal cell carcinoma, superficial bladder tumors \[Ta and Tis\] or any cancer curatively treated \> 5 years prior to randomization. * Known or suspected allergy to sorafenib or gemcitabine/capecitabine. * Prior or concurrent use of St. John's Wort or rifampin (rifampicin) within 3 weeks of randomization. * Concurrent anti-cancer therapy other than gemcitabine/capecitabine and sorafenib/placebo. * Prior treatment with any agent that targets VEGF or VEGFR (licensed or investigational), except bevacizumab. * Women who are pregnant or breast-feeding. * Use of any investigational drug within 30 days or 5 half-lives, whichever is longer, preceding randomization. * Inability to comply with protocol and/or not willing or not available for follow-up assessments. * Any condition which in the investigator's opinion makes the patient unsuitable for the study participation.