And what a memorable Mariners debut he delivered with the bat, behind the plate catching ace Felix Hernandez, and even in a spontaneous mound visit.
Blanco hit a sixth-inning grand slam to break a scoreless tie and give Venezuelan countryman and good friend King Felix all the offense he needed, and Seattle beat the Oakland Athletics for the second straight game with a 4-0 victory Saturday.
He hardly saw this coming.
"I was hoping I could still get a job and show them I can still play," said Blanco, who is playing for his 11th team. "That was a special day today."
The 41-year-old Blanco, a .184 hitter with no home runs coming into the game, was a most unlikely candidate to provide the decisive hit for Seattle. The Mariners signed him Friday, three days after his release by Toronto. He became the oldest Seattle player ever with a slam.
Mariners manager Eric Wedge wrote Blanco into the lineup right away and it didn't hurt Blanco had previously caught Hernandez in the bullpen for the World Baseball Classic.
"I'm glad he did it," Wedge said. "First of all, I thought he did a tremendous job behind home plate. You can see what he does back there, how he handles things and the way he makes it look so easy. ... Talk about going up there ready to hit, bases loaded, he goes up there ready to hit and hit it a long way."
Hernandez (8-4) struck out five of Oakland's initial eight batters and seven through four innings on the way to eight Ks in seven scoreless innings.
Michael Morse had two doubles among his three hits, including one in the sixth before Blanco's drive stayed just inside the left-field foul pole.
Blanco's only other grand slam came with Milwaukee more than 13 years ago on May 12, 2000, off Pittsburgh's Jason Schmidt. It was the fifth-longest gap between grand slams dating back to 1900, according to information provided by the Mariners from the Elias Sports Bureau 13 years, 34 days.
Blanco's slam at 41 he turns 42 on Aug. 29 topped one by Raul Ibanez earlier this season accomplished at 40 years, 347 days.
"That's pretty good. We'll I've got it now," Blanco said, smiling.
Hernandez received a big defensive assist to end the fifth and save a run.
Jed Lowrie doubled leading off the inning and advanced on Seth Smith's flyout to center. But Chris Young flied into a double play in which right fielder Endy Chavez threw Lowrie out at home to keep the game scoreless. Lowrie didn't even touch the plate.
"I called him out," Hernandez quipped.
And, with Coco Crisp aboard on a one-out single in the sixth, Hernandez got John Jaso who caught his perfect game with Seattle last year to line into a double play at first that caught Crisp off the bag. The A's also grounded into an inning-ending double play in the seventh with runners on first and second.
Suddenly, Seattle has a chance to sweep the first-place A's on Sunday after Oakland took three in a row from the New York Yankees before this series began, including a 3-2, 18-inning victory Thursday.
Seattle snapped Oakland's 11-game home winning streak at the Coliseum on Friday night, then put together another fine performance to back its ace. The A's have lost their first series in the last 10 over the past month.
Hernandez allowed five hits and walked one to improve to 22-7 with a 2.70 ERA lifetime in 39 career starts in June. Seattle starters are 5-1 with a 0.94 ERA 6 earned runs in 57 1-3 innings since June 7 and have gone six straight starts of at least seven innings.
Charlie Furbush and Yoervis Medina each pitched an inning of relief to finish the Mariners' six-hit shutout.
Still, Blanco provided the highlight of the day.
"For him to come through like that is awesome, his first start here. That was unbelievable," Hernandez said. "It surprised me a little bit. But I know he has a little power. He's good."
Oakland's A.J. Griffin (5-6) dropped to 0-3 over his four-start winless stretch. The right-hander allowed four runs and eight hits in six innings, struck out three and walked two.
"At the end of the day it's four runs on one pitch, and when you're facing Felix, every run counts," Griffin said. "It's frustrating. Hopefully we're not talking about something like this again."
Blanco, meanwhile, hopes for a few more. In his 16th season, he is still fueled by one thing:
"I'm just trying to win a World Series," he said. "I love the game, I have passion for the game and I just want to get a ring so I can go home."
Notes: Crisp returned to the Oakland lineup playing center field and batting leadoff in his first start since bruising his heel Tuesday night against New York. He didn't move as well as usual. ... A's RF Josh Reddick had the night off. ... Mariners starting pitchers have had eight consecutive quality starts. ... Wedge said 1B Justin Smoak (strained right oblique), CF Franklin Gutierrez (strained right hamstring) and demoted 2B Dustin Ackley would likely be re-evaluated after Sunday's game to determine their next steps. ... The series finale Sunday has the looks of a possible pitcher's duel with Oakland's Bartolo Colon (8-2) and Seattle's Hisashi Iwakuma (7-1). ... Announced first-pitch temperature was 56 degrees. ... In 2001, Edgar Martinez hit a grand slam at 38 years, 220 days the previous-oldest Seattle player before Ibanez and Blanco this season.