Richard Williams, Serena’s father, took the high road yesterday after a series of blown third-set line calls doomed his daughter in Tuesday night’s quarterfinal loss to Jennifer Capriati.

Papa Williams has often been critical of the tennis establishment, believing it is against the Williams sisters because of their race. Chair umpire Maria Alves of Portugal, now banished from the Open, made a bizarre overrule in the first game of the deciding third set last night on a ball that was inside the line. Then, in the match’s last game, the three close calls that went against Serena all were proven to be ruled incorrectly after television replay.

However, through his associate Leland Hardy, Papa Williams was extremely gracious amid the heartbreaking 2-6, 6-4, 6-4 loss.

“It was human error,” he said. “If I was sitting in the same umpire chair, I’ve could’ve made the same call perhaps, because it’s the human eye. I don’t have anything against the umpire. The key element is in the amount of unforced errors.”

The restraint Papa Williams showed was surprising, considering earlier this week he shared his belief that the “system” was still against his daughters.

“When Venus and Serena were winning, there was something wrong,” Papa Williams told The Post Sunday. “When they’re losing, there’s something wrong. Very honestly, it’s a disgrace. I think it’s a disgrace at how the system is against those two black girls. If they win, everything is wrong, if they lose, it’s get rid of the parents. I just work for them. They’ve always wanted me around.”

After the match, Serena said she felt, “bitter, cheated and robbed,” mentioning the third set felt similar to the “conspiracy at Wimbledon with Venus” when the game score was announced inaccurately and not in Venus’ favor at a crucial juncture of the match.

Meanwhile, Papa Williams is hoping his daughters quit tennis to become entrepreneurs. Both have struggled with injuries recently and Serena still hasn’t recovered 100 percent from knee surgery a year ago.

Papa Williams believes his daughters are so gifted mentally, they can make more money as investors.

“I’d like to see them quit and do something else,” Papa Williams told The Post earlier this week. “It’s a shame for them to waste those great minds on hitting a tennis ball.”

He said he’s had success as an entrepreneur in recent years. “I know I can match dollar to dollar with anyone here,” he said. “That’s what I love to talk about – money. Not because I teach tennis [but] because of how brilliant I’ve been in other business ventures.”

In some ways, Serena seems bored with tennis, shown in her decisions to wear rebellious outfits such as denim skirts, “micro-mini shorts” and knee-high black boots during the fortnight in lieu of comfort. At one point, she even said she enjoyed talking about her clothes more than the tennis.