SAN FRANCISCO — With two exciting young prospects joining the roster Monday, the Giants parted ways with a veteran outfielder and sent another to Triple-A. Jerar Encarnación was designated for assignment and Will Brennan was optioned back to Sacramento, opening roster spots for Bryce Eldridge and Jesús Rodríguez, who were officially called up as part of a roster shakeup following a winless six-game road trip. Eldridge will be starting his second stint in the big leagues, with the organization hoping he’s up for good. Rodríguez’s first game action will be his MLB debut. The Giants also put lefty Erik Miller on the IL with a lower back strain. That opened a roster spot for Trevor McDonald, who will start Monday’s game. Encarnación is out of options and was DFA’d after hitting .176 with just one extra-base hit in 17 appearances. The 28-year-old occasionally flashed intriguing power in parts of three seasons with the Giants and was well-liked in the clubhouse, but he had trouble staying on the field, and he ended up posting a .619 OPS in scattered playing time. The Giants chose Encarnación...