Write SQL query to solve given problem: In what year did the only team to beat the Houston in the final round of postseason series games earn its lowest ranking?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T2.year FROM series_post AS T1 INNER JOIN teams AS T2 ON T1.tmIDWinner = T2.tmID WHERE T1.round = 'DSF' AND T1.tmIDLoser = 'HSM' ORDER BY T2.rank ASC LIMIT 1