The Arrillaga Center basketball courts were transformed yesterday into the site of one of the Bay Area’s largest blood drives.

For the last three years, Stanford and Cal have taken part in “Rivals for Life,” a contest to see which school can collect the most units of blood over the course of a day. Held during Big Game Week, the competition capitalizes on intensified school spirit as Stanford unites to beat Cal in the Saturday football game.

“Not only can you help save a life today, but you can help us beat Cal,” Stanford Blood Center account manager Elisa Manzanares said in an appeal to potential donors.

Cal won the first “Rivals” blood drive in 2007, but Stanford has prevailed in the last two years. Last year, Stanford won by a close margin of 260 to Cal’s 251 units of blood.

Manzanares said Tuesday’s turnout was good, with roughly 266 units collected. The results, however, remain unofficial until the blood is processed in a lab to determine the exact volume of usable specimens.

Over the past few weeks, Manzanares sent out e-mails to all the resident assistants (RAs) on campus, who in turn encouraged their respective dorms to donate by writing on whiteboards, engaging students in conversation or making announcements during dorm meetings.

“It’s because of the RAs that I think we win,” Manzanares said. She added that among students, the freshman class has participated most widely in all the blood drives to date, while seniors and graduate students have had the weakest turnouts. University staff members, however, have come out in the greatest numbers of all.

“Our staff and faculty contribute about 40 percent of the units collected,” Manzanares said.

Stanford has been able to win the competition the last two years despite the fact that its population is less than half of Cal’s. Eric Stein, senior associate athletic director for recreation and wellness, attributes this success to Stanford’s efforts at publicizing and collaborating on the event.

“It’s exciting that we have a team effort where we’re working with students, faculty and staff to try to create the biggest blood drive in the entire Bay Area,” Stein said. “It’s been a great process. We’ve opened up the Rec Center. While it used to be done on smaller venues on campus, today to see two courts and every single station being utilized is fantastic.”

At the event, in the middle of the courts, about a dozen nurses in white lab coats hovered over several rows of donors in reclining chairs.

According to Manzanares, blood donations are necessary for patients who can require many units at a time, depending on the severity of their conditions. A cancer patient needs one or two units per week (a unit is equivalent to one pint of blood, the amount supplied by a regular donor), while an automobile accident victim can require up to 50 units at one time.

The Stanford Blood Center is a nonprofit that collects several hundred units a day — roughly as much as “Rivals for Life” yields — at its center and in its mobile “Bloodmobiles” deployed throughout the Bay Area. The center is unique because in addition to supplying blood to hospitals for use in transfusions, it also provides platelets to local companies who conduct cutting-edge research to develop new life-saving therapies and treatments, Manzanares said.

Despite the success of the blood drive and the efforts of the Stanford Blood Center in general, there is still an overall shortage of platelets locally and nationwide.

“Only two to three percent of the population in the Bay Area donate,” Manzanares said. “It’s not that they don’t care, but that the society is too fast-paced.”

She’d like to see more people showing up and, just as importantly, donors coming in for repeat visits. “If all donors donated twice a year, we wouldn’t have nearly as much of a shortage,” Manzanares added.

This Thursday Cal hosts its blood drive, after which a winner will be declared — all in time for the Big Game.