The Mariners haven't won since as they head into Friday night's rematch between the two pitchers in the opener of a three-game series on Friday night at Fenway Park.
The Red Sox won the Sunday game in Seattle and then lost the first two games in Minnesota before rebounding a 9-2 win and Rick Porcello's ninth win of the season on Thursday.
After losing the game Sunday, the Mariners were swept in a three-game series by the Yankees in the Bronx -- to start a difficult 10-game swing through the East that concludes with a four-game series in Baltimore.
LeBlanc, who has been pitching well in his latest role, is 3-0 with a 2.63 ERA and has yielded only 11 earned runs in nine starts -- capped by 7 2/3 shutout innings (two hits, no walks, nine strikeouts) against the Red Sox.
He is just 33-35 with a 4.23 ERA in his career, but much of the negative numbers are in the past -- at least for now.
After beating the Red Sox, he said, "That's a stout lineup over there, but the fact that me and Z (catcher Mike Zunino) were able to mix things up and put them in the rocking chair makes things easier. Everything was executed and that's really all I can say. It's the most important thing for me -- it's to execute pitches. Today, me and Z were able to do that."
But the team has faltered since, blowing a 5-0 lead in Wednesday's game before losing 4-3 on Thursday.
"Coming in here, we have been playing very good baseball," said Seattle manager Scott Servais, whose team has dropped five of its last seven. "We know what kind of ballclub they have with the power and the bullpen. I thought we were right in the game the last couple of days.
"But you have to hit on the road. You have to get big hits on the road. We just didn't get it done. It doesn't detract or take away from anything that we've done to this point. Our guys are not down at all."
The Boston bats snoozed through the first two games in Minneapolis, wasting starts by Chris Sale and David Price. The bats broke out Thursday, avoiding the sweep and leaving the Red Sox (50-26) as one of three American League teams with 50 wins.
"I think it was just a couple of tough days," Mookie Betts, who hit is 19th homer of the season Thursday, said after the game. "We came out ready to swing it and it just showed what we can do."
Wright has been outstanding since making his delayed 2018 debut (after knee surgery and a 15-game MLB suspension). He is 2-1 with a 1.23 ERA and gave up just the one losing run in the matchup with LeBlanc.
"He's been great. Outstanding, really," Cora said. "I heard a lot of good things about him before I got here and he's showed why."
He is 2-2 with a 1.31 ERA in four games (two starts) against the Mariners. Kyle Seager is 3-for-9 and Nelson Cruz 2-for-6 (both .333), and Zunino is 1-for-8 (.125) and Dee Gordon 1-for-6 (.167) against the knuckleballer.
LeBlanc is 1-0 with a 3.24 ERA in three career starts against Boston. The Current Red Sox roster is a combined 3-for-16 against him. J.D. Martinez is 2-for-3 (.667) and no one has with more than three at-bats against him.