Baseball-Major League Baseball roundup

July 30 (The Sports Xchange) - The Washington Nationals addressed their struggling bullpen by acquiring All-Star closer Mark Melancon from the Pittsburgh Pirates, the teams announced Saturday. The Pirates received left-handed reliever Felipe Rivero and minor league left-hander Taylor Hearn as part of the trade. The 31-year-old, right-handed Melancon is 1-1 with a 1.51 ERA and 30 saves in 45 appearances this season. He is a three-time All-Star with a 2.65 career ERA and 151 saves in eight seasons with the New York Yankees, Houston Astros, Boston Red Sox and Pirates. He saved a league-high 51 games in 2015. Melancon is expected to serve as the closer for the Nationals after veteran closer Jonathan Papelbon struggled to close out games in the ninth over the past week. - - - The San Francisco Giants activated outfielder Hunter Pence from the 15-day disabled list after being out for two months with a torn hamstring. Pence tore his right hamstring off the bone while running the bases during a game on June 1 and had surgery a week later. Before going on the disabled list, Pence was batting .298 with seven home runs and 36 RBIs. The Giants designated infielder Ramiro Pena for assignment to make room for Pence on the active roster. - - - The Seattle Mariners placed right-handed pitcher Nathan Karns on the 15-day disabled list with a low back strain. Karns, 28, is 6-2 with a 5.15 ERA over 94 1/3 innings with 101 strikeouts and 45 walks in 22 games this season. The Mariners also recalled right-hander Cody Martin from Triple-A Tacoma. - - - Chicago Cubs first baseman Anthony Rizzo was held out of the starting lineup Saturday after starting the previous 30 games in a row. Rizzo has played 99 games this season, which is second on the team to third baseman Kris Bryant. "He has really been needing a day (off)," Cubs manager Joe Maddon said. "We rely on him so heavily." (Editing by Andrew Both)