SAN DIEGO (Interstat) — The St. Louis Cardinals and San Diego Padres open a four-game series Thursday night at PETCO Park, with the first-place Padres looking to maintain their narrow edge atop the National League West. San Diego (22-14) enters with the best record in the division, one game ahead of the Cardinals (21-15) in the standings. The Padres are coming off a 5-1 victory Wednesday at San Francisco, while St. Louis dropped a 6-2 decision at home to Milwaukee. Right-hander Michael King (3-2, 3.86 ERA) will start for San Diego. He has posted quality starts in three of his last four outings. The Cardinals will counter with left-hander Matthew Liberatore (1-1, 4.15 ERA), who is seeking his second win of the season. Players to watch For St. Louis, left-handed reliever Jared Shuster has been effective in recent appearances. Over his last two outings, Shuster has pitched 4.0 scoreless innings, allowing one hit with one strikeout. He worked 2.0 hitless innings Tuesday against Milwaukee. For San Diego, right-hander Matt Waldron delivered a strong start Wednesday at San Francisco, throwing 5.0 innings of two-hit ball, allowing one earned run with seven strikeouts to earn the win. Over his last two starts, Waldron has a 2.70 ERA with 10 strikeouts in 10.0 innings. Recent form St. Louis has won six of its last nine games, including a three-game sweep at Pittsburgh from April 27-29. The Cardinals’ offense has averaged 5.1 runs over that stretch. San Diego has won three of its last four, including a series victory at San Francisco. The teams will play four games in three days, with a traditional doubleheader scheduled Saturday. After this series, St. Louis travels to Oakland for three games, while San Diego visits Milwaukee for three. Game notes The Padres are installed as -1.5 run-line favorites, according to Interstat’s projections, with an over/under of 8. The simulator forecasts a 7-4 Cardinals victory, though San Diego has won five of its last seven at home. First pitch is scheduled for 7:10 p.m. EDT. The game will be broadcast on MLB Network and local affiliates.