One Medical Group is in growth mode, and now says it will open three new primary care offices in the Phoenix area over the next few months.

The group, which claims to be the fastest-growing primary care system in the country, says the offices will be in Phoenix, Gilbert, and Scottsdale. It’s also signed a big-league client: the Arizona Diamondbacks of Major League Baseball.

“Given the strong demand for high-quality primary care in this rapidly growing market, Arizona appears to be a natural fit for One Medical,” said One Medical founder and CEO Tom Lee. “… We hope to improve the quality and value of health care in this market.”

One Medical is partnering with Dignity Health in Arizona, and the two say they have other initiatives in the works as well.

Dignity Health is interested in providing its patients with access to One Medical’s take on health care. One Medical’s technology-enabled approach gives doctors and other care givers advanced diagnostics and medical records tools, and uses things like virtual doctor visits to make it easier for patients to access care.

For employers, One Medical has become a premium perk – sort of like a gym membership — for employees.

Dignity Health, which is rapidly expanding in Arizona, now includes five hospitals and dozens of clinics and other medical partnerships. Dignity will connect One Medical to its network of affiliated physicians and resources through the Arizona Care Network, the companies say.

The Arizona Diamondbacks have signed on as One Medical’s first enterprise customer in Arizona. One Medical is now the official “Primary Care Physician” of the Arizona Diamondbacks (it’s common for sports teams to take up such sponsorships with health care providers).

During 2014, One Medical added six new locations (including a flagship office in Los Angeles) and launched an employer-focused primary care offering that is now being used by over 100 enterprise clients nationwide.

Founded in 2007, the San Francisco-based startup has raised a total of $117 million in funding to date.