The Braves continued locking up players to long-term deals by signing third baseman Chris Johnson to a three-year, $23.5 million extension that includes a $10 million team option for 2018. He’s the sixth Braves player signed to multi-year extension in the past three months. After finishing second in the National League batting race with a .321 average in 2013, Johnson is off to a slow start in his second season with the Braves, batting .255 with six doubles, one home run, four RBIs and a .290 on-base percentage in 26 games. He’s a .286 career hitter in the majors with a .326 OBP, 111 doubles and 46 homers in 516 games and nearly 2,000 plate appearances. “Chris has proved over the last year to be a valuable member of our team,” Braves general manager Frank Wren said in a prepared statement. In addition to batting average, Johnson set career-highs last season in doubles (34), OBP (.358), games played (142) and plate appearances (547), after coming to the Braves as what was widely characterized as a “throw-in” part of the trade for Justin Upton. Johnson began the 2013 season in a third-base platoon with Juan Francisco, but played so well early that he took over the full-time job and the struggling Francisco was traded in June.