Relief pitcher Willie Hernandez says he will accept a $4.5-million contract offer with Detroit Tigers if the baseball club meets two conditions. One of the conditions for signing the four-year pact, he said yesterday in Puerto Rico, is that the club establish a 12-year system of deferred payments. He also wants the team to guarantee, during the last two years of the pact, that his salary will remain at least equal to salary of other Tiger pitchers. ” would sign the contract right now, if Detroit accepts a clause to pay me in the last two years the same money that whatever free agent signs that surpasses my salary,”he said. ” want the deferred payments to assure the future of myself and my family.” Hernandez, who had 32 saves and a 1.92 earned-run average in leading the Tigers to the American League pennant and the World Series title, has been seeking a four-year contract for $5-million. The lefthander would become a free agent March 15 unless he signs with Detroit. U. L. Washington will be sent to the Montreal Expos by the Kansas City Royals, according to a report in The Kansas City Star.