The Pittsburgh Pirates are making a charge up the National League standings and a return to form by Francisco Liriano would go a long way toward their goal of reaching the postseason for a second straight year. Liriano, who won 16 games in 2013 to lead the Pirates to their first playoff berth in 21 years, has only two wins this season entering Tuesday's start at the San Francisco Giants. The Pirates have won seven of 10 to close within two games of Central-leading Milwaukee.The Giants are careening in the opposite direction, having lost five straight to drop two games behind the first-place Los Angeles Dodgers in the NL West. Monday's 5-0 loss to Pittsburgh was the second shutout in five games for San Francisco, which has been outscored 24-5 during the five-game skid. Hunter Spence is mired in a 2-for-20 slump, catcher Buster Posey has two hits in his last 17 at-bats and Brandon Crawford and Tyler Colvin are each in 3-for-17 ruts.TV: 10:15 p.m. ET, MLB Network, ROOT (Pittsburgh), CSN Bay Area (San Francisco)PITCHING MATCHUP: Pirates LH Francisco Liriano (2-7, 4.18 ERA) vs. Giants RH Tim Hudson (8-7, 2.65)The All-Star break came at a much-needed time for Liriano, who has started to bury the memories of a dreadful first half by allowing one earned run in his last two turns. He won for the first time since May 30 last time out, limiting the Los Angeles Dodgers to one run and four hits over a season high-tying seven innings. Liriano is 1-1 in two starts versus the Giants but has permitted eight runs and 17 hits in 10 innings.Hudson has taken a few steps back after a stirring first 2 1/2 months in which he posted a 7-2 record and major league-leading 1.81 ERA. Hudson is 1-5 over his last seven starts but hasn't received much help from San Francisco's offense, which has scored a combined four runs in his last four defeats. He has lost three consecutive starts at AT&T Park after opening the season 5-0 in his first seven turns there.WALK-OFFS1. Pirates LF Josh Harrison is 6-for-9 with two homers, three RBIs and four runs scored in his last two games.2. The Giants are 6-20 in their last 26 home games.3. Pirates CF and reigning NL MVP Andrew McCutchen is 2-for-21 in his last six games.PREDICTION: Giants 3, Pirates 1