Brock Nelson’s last-minute assist ensured that he and teammate Ilya Sorokin would each reach impressive career milestones Saturday night — and that the New York Islanders would complete a much-needed third-period shutdown effort.The Islanders will aim to establish some momentum Monday night, when they host the Detroit Red Wings in a battle of Eastern Conference rivals in Elmont, N.Y.Both teams were off Sunday after playing at home Saturday night, when the Islanders beat the St. Louis Blues 3-1 and the Red Wings fell to the Boston Bruins 2-1.The win snapped a three-game losing streak (0-2-1) for the Islanders, who squandered a third-period lead in each defeat — including Thursday night in Detroit, when the Red Wings scored twice in the final 4:46 to earn a 2-1 win.The final 20 minutes began in familiar fashion Saturday night for the Islanders, whose 2-0 lead was cut in half when Jake Neighbours scored a power-play goal for the Blues just 45 seconds after the opening faceoff.But goaltender Sorokin stopped the final eight shots he faced, including Neighbours’ wrister with 1:39 left after the Blues pulled goalie Jordan Binnington. Nelson helped ice the win with 37 seconds left, when he fed Kyle Palmieri for the empty-netter.”Obviously, the way the last couple games have gone, our goalies have given us a chance to win and we haven’t found a way to get the insurance,” said Palmieri, who also scored in the first period in his first multi-goal game of the season. “So it felt good to do that tonight.”Nelson, 33, who scored the Islanders’ second goal in the second period, finished with three points Saturday to increase his career total to 544 points and move into a tie for ninth place on the Islanders’ all-time list with John Tonelli. The win was the 100th for Sorokin, 29, who is the sixth New York goalie to reach the century mark.