Lefty Joe Saunders almost always pitches well at Safeco Field, where he’s 10-2, 2.31 in his career. / Drew Sellers, Sportspress Northwest

GAME: Pirates (46-30, 2nd, NL Central, -1.0 GB) at Mariners (34-43, 3rd, AL West, -10.5 GB). GAME #: 78. SERIES: 1st of 2 games. MEETING: 3rd (series tied 1-1). WHEN: Tuesday, 7:10 p.m., Safeco Field. STREAKS: Mariners W 2; Pirates W 4. TV: Root Sports. RADIO: ESPN 710, Mariners Radio Network

While the Mariners continue to have their ups and downs — they are currently on an “up” with a two-game winning streak — the Pittsburgh Pirates are enjoying a charmed season. As bad or worse than the Mariners for the past decade, the Pirates stand second in the NL Central with 46 victories — and second in all of MLB. Their two-game series Seattle Tuesday comes after a sweep of the Angels in Anaheim.

One reason for Pittsburgh’s success is the All-Star-caliber season that 25-year-old lefty Jeff Locke is having. A cameo pitcher in 2011 and 2012 when he largely was knocked around, Locke ranks second in the National League with a 2.01 ERA and is 10th in WAR at 2.4. He has held opponents to a .235 batting average on balls in play (second lowest in the NL) and allows 6.2 hits per nine innings, fifth best in the majors.

Locke, who has never faced the Mariners, has allowed zero runs in seven of his 15 starts, one run in three others and three hits or fewer eight times. In his six wins, he has allowed just one earned run. All the numbers that suggest Tuesday’s series opener shapes up as a pitching duel.

Lefty Joe Saunders has a 1.82 ERA over his past five starts, but won only twice thanks to limited run support, including a 1-0 complete-game loss in Anaheim Thursday. The 31-year-old is 10-2 with a 2.31 ERA in 16 career starts at Safeco Field.

After winning in 10 innings Sunday on Kendrys Morales’ 10th-inning walk-off homer, the first such hit by a Seattle batter since 2011, the Mariners again seek a third consecutive victory. They haven’t won three in a row since May 1-4.

The Mariners and Pirates are playing for the second time this season. The clubs split a pair at PNC Park May 7-8.

TUESDAY’S PROBABLES

MARINERS: LHP Joe Saunders (5-7, 4.48 ERA, 1.39 WHIP)

The 32-year-old Saunders, a Springfield, VA., native in his ninth major league season and first with Seattle, makes his 16th start and first against the Pirates. Saunders has a 1.82 ERA over his past five starts, but won only twice due to limited run support. In his last start at Safeco Field June 8, Saunders was backed by just one run in a 3-1 setback to the New York Yankees. Saunders is 10-2 with a 2.31 ERA in 16 career starts at Safeco Field, including 4-2, 2.53 this season.

• LAST START: June 19, lost to the L.A. Angels 1-0 despite a complete game; 1 earned run on 6 hits in 8.0 innings; 3 strikeouts, 2 walks, 100 pitches, 58 for strikes.

• LAST VS. PIRATES: Aug. 9, 2012, won 6-3; 3 earned runs on 7 hits in 7.0 innings; 3 strikeouts, 0 walks, 115 pitches, 77 for strikes.

• CAREER VS. PIRATES: 2-0, 3.15 ERA in 3 starts covering 20.0 innings; 11 strikeouts, 2 walks, 1 home run, 1.10 WHIP.

• AT SAFECO FIELD: 10-2, 2.31 ERA in 16 starts covering 101.1 innings; 54 strikeouts, 32 walks, 7 home runs, 1.13 WHIP.

• LOVES TO FACE: Josh Harris (0-for-7, .000), Clint Barmes (1-for-10, .100), Brandon Inge (4-for-22, .182).

• HATES TO FACE: Neil Walker (2-for-5, .400), Jerry Sands (4-for-11, .364), Russell Martin (3-for-9, .333).

• CURRENT PIRATES VS. SAUNDERS: 26-for-103, .252 BA, 18 strikeouts, 4 walks, 3 home runs, .278 on-base percentage.

PIRATES: LHP Jeff Locke (6-1, 2.01 ERA, 1.13 WHIP)

The 25-year-old Locke, a North Conway, NH., native in his third major league season, all with Pittsburgh, will make his 16th start and first against the Mariners. He ranks second in the majors in ERA at 2.01. After losing his first start of the season to the Dodgers April 7, Locke has won six consecutive decisions. He also has eight no-decisions. The Atlanta Braves selected Locke in the second round of the 2006 amateur draft. The Braves traded Locke to the Pirates as part of a package June 3, 2009.

• LAST START: June 19 at Cincinnati, took a no-decision in Pittsburgh’s 2-1 loss; 0 earned runs on 4 hits in 7.0 innings; 3 strikeouts, 3 walks, 95 pitches, 57 for strikes.

• LAST VS. MARINERS: Never faced.

• CAREER VS. MARINERS: No record.

• AT SAFECO FIELD: Never pitched.

• LOVES/HATES TO FACE: Locke has never faced a member of the Mariners roster.

MARINERS STATS / NOTES

• CURRENT HOME STAND: Three vs. Oakland (Friday-Sunday), two vs. Pittsburgh (Tuesday-Wednesday), three vs. Chicago Cubs (Friday-Sunday). Following the home stand, the Mariners have a six-game road trip through Texas and Cincinnati.
• Raul Ibanez, who belted two home runs Sunday, has eight home runs in June and is the second-oldest player to deliver a multi-homer game wearing a Mariners uniformm at 41 years, 21 days. Edgar Martinez was 41 years, 250 days when he hit a pair of long balls Sept. 8, 2004 against Cleveland. Ibanez is also the first 41-year-old with a multi-homer game since Barry Bonds and Moises Alou (two each) in 2007.
• Ibanez is sixth on the Mariners all-time home run list with 144, ahead of Bret Boone (143). Ibanez is batting .321 over his last seven games.
• Ibanez has 17 home runs. The record for a 41-year-old is 29 by Ted Williams in 1960.
• The walk-off home run by Kendrys Morales Sunday was the first by a Seattle player since Luis Rodriguez Sept. 14, 2011 against the Yankees.
• Oliver Perez has not allowed an earned run in his past 13 outings. During that stretch, he has lowered his ERA from 1.05 to 0.98.
• Jeremy Bonderman has allowed just four earned runs over his past four starts. He has a 1.42 ERA during that stretch.
• Endy Chavez has a hit in 17 of his past 19 games and is batting .303 over that span.

UPCOMING PROBABLES