PITTSBURGH — The Pittsburgh Pirates insist they’re not scoreboard watching as they try to chase the franchise’s first playoff berth in 21 years.

Good idea. At the moment the teams in their rearview mirror are inching closer by the day.

Jeff Locke’s second-half struggles reappeared and Pittsburgh’s offense again fell silent in a 5-2 loss to the San Diego Padres on Tuesday night.

The Pirates began the day tied with St. Louis for the NL Central lead but allowed Cincinnati and Washington — both in pursuit of playoff berths — to gain ground.

“Everybody’s aware of where we are, what’s going on,” Pirates manager Clint Hurdle said. “At the end of the day, we had a couple of opportunities we didn’t maximize on.”

A night after getting one-hit by San Diego’s Andrew Cashner, Pittsburgh managed just two runs against easy throwing Eric Stults (9-13).

The left-hander’s fastball only tops out in the mid-80s but kept the Pirates off balance by throwing a bevy of offspeed stuff that included a pair of changeups in the mid-60s.

“He’s learned how to pitch,” Hurdle said. “At the end of the day we’ve got to continue to work hard to get the most out of our offense.”

Andrew McCutchen went 2 for 3 and Marlon Byrd drove in both of Pittsburgh’s runs, but the Pirates continued to have problems with the Padres.

San Diego improved to 30-10 at PNC Park since it opened in 2001 by getting to Locke.

A surprise All-Star in July, Locke again had problems with his command, allowing four runs and seven hits in five innings, striking out five and walking three. Locke is just 2-4 since mid-July.

“This ain’t no different than all the other starts,” Locke said. “Just falling behind early and getting behind.”

Jedd Gyorko blasted a 3-run homer among his three hits and Ronny Cedeno also had three hits for San Diego. Luke Gregerson worked the ninth for his fourth save as Stults won for the first time since July 17.

“It’s definitely good to get one,” Stults said. “It’s one of those things that maybe it’ll be a little confidence boost, I’ve thrown some games where I’ve had some tough luck and others where I’ve put in a position to win and it just didn’t happen.”

Stults was winless in his previous 10 starts and came in with a 3-9 mark on the road.

Still he never let the Pirates get comfortable, testing their patience behind a steady diet of offspeed stuff that wouldn’t have broken the speed limit on most interstates.

At one point he retired Pedro Alvarez on a 66 mph changeup then dropped it down to 64 mph to get Josh Harrison to ground meekly to third. It was enough to prevent one of the National League’s top-hitting teams against left-handers from cashing in.

“We had a rough game,” Pittsburgh first baseman Gaby Sanchez said. “We’ll try to go shower it off and win tomorrow.”