Locke tries to lead the visiting Pirates to a season-high fifth consecutive win Tuesday night in the opener of a two-game set against the Seattle Mariners.Alvarez homered for the fourth straight game before Pittsburgh (46-30) scored a combined seven runs in the ninth and 10th innings during Sunday's 10-9 road win over the Los Angeles Angels."I got to hang out in the air conditioning in here for about six innings, so I felt fresh when I got out there," said Russell Martin, who went 2 for 2 with two RBIs after coming on as a pinch-hitter in the ninth. "But our guys battled back and had great ABs collectively, top to bottom, and it was fun to be a part of. We have no quit, that's for sure."The Pirates, averaging 6.5 runs during the win streak, went 6 for 16 with runners in scoring position Sunday. Pittsburgh has won four straight three times but hasn't posted five consecutive victories since July 17-22."When those guys get guys on base, they take advantage," Angels reliever Kevin Jepsen said. "That's why they're playing as well as they are."Much of the Pirates' recent success can be attributed to Alvarez. The slugging third baseman has raised his average 25 points to .237 while going 13 for 33 with five homers and 13 RBIs during an eight-game hitting streak.Alvarez, whose nine home runs since June 2 rank second in the majors, will try to become the first Pirate to homer in five straight games since Jose Castillo from May 26-31, 2006.Locke (6-1, 2.01 ERA), meanwhile, has shined on the mound. The NL leader in ERA is 6-0 with a 1.73 ERA over 14 starts since taking the loss in his season debut April 7, giving up one or zero runs in six of his last seven outings.Locke yielded four hits over seven scoreless innings Wednesday in a 2-1, 13-inning loss at Cincinnati. The left-hander has received an average of 2.59 runs of support in his last nine starts."I know that I've got guys here I got to do my best to take care of, because they're taking care of me," he told MLB's official website.Locke will try to quiet a Mariners team coming off a thrilling victory of its own, 6-3 over Oakland on Sunday. Raul Ibanez hit a pair of homers before Kendrys Morales delivered a pinch-hit game-winning three-run shot in the 10th inning.Ibanez is hitting .288 with six homers and 12 RBIs in his last 13 games."I'm just trying to hit the ball on the barrel and things are working out," he said.The Mariners (34-43) now turn to Joe Saunders (5-7, 4.48), who dropped to 2-2 with a 1.82 ERA over a five-start stretch after going the distance in Wednesday's 1-0 loss at Los Angeles."Joe was good," Angels manager Mike Scioscia said. "His fastball had a little more life than a couple years ago, so he's feeling pretty good right now and he pitched a strong game for those guys."Saunders also thrived in two starts against the Pirates while with Arizona last year, winning both while compiling a 1.93 ERA. He'll need to be careful against Gaby Sanchez, who is 6 for 12 with a homer in their matchups.