Returning to the dugout after the fourth inning, Blanton let loose on the dugout cooler, then he and catcher Chris Iannetta became involved in a heated discussion with pitching coach Mike Butcher intervening.
"Anytime things aren't going good, it kind of bring things to a little volcano, a head, whatever you want to call it," said Blanton, who finished the first half with a 2-12 record and 5.53 ERA. He has never lost more than 13 games in any of his 10 seasons in the big leagues.
In regards to the confrontation, Iannetta said it was, "something between us. Not really that big a deal... just some things that happened."
The root cause of the shaky outing was likely tied to the fact that Blanton had a severely limited pitching arsenal.
"All I could throw today was the fastball. That makes it tough when I didn't have my change or curveball, either one," he said. "That usually doesn't happen, but it did today."
"It just kind of happened out there. I'd throw [the changeup] down and it's in the dirt. I throw it up and it goes off. I couldn't get in between today."
Blanton had his shortest outing of the season -- four-plus innings. He allowed four runs on five hits, walked four and struck out two.
"It is what it is," he said when asked if the confrontation in the dugout is behind him. "Things aren't going well. It's a long season. You try to do more. You're out there competing with everything you have. Things happen.
"Guys get mad when they're giving up runs. Guys get mad when they strike out. Guys get mad for a ton of different reasons when you're playing the game. It's part of it sometimes."
Mark Trumbo homered and Alberto Callaspo had two RBIs, but the Angels could not crack Mariners right-hander Hisashi Iwakuma.
Trumbo hit his 21st home run on the first pitch to open the fifth, making it 3-1. It was his fourth homer against the Mariners this season.
The Mariners would push ahead, 4-1, in the bottom of the inning on an RBI double by Raul Ibanez, but Callaspo answered with a bases-loaded, two-run single in the sixth to close it to 4-3.
The Angels could not rally again off Charlie Furbush and Tom Wilhelmsen, who picked up his 19th save in 23 opportunities.
It was the fourth time the Angels have been swept this season, the first time on the road.
"That's a big win for us, especially going into the break," Mariners manager Eric Wedge said. "It's something we haven't done this year. It's hard to win a series. It's real hard to sweep, whenever you do that, you make up some ground."
Josh Hamilton and Albert Pujols were a combined 3-for-23 in the series with one RBI and eight strikeouts.
Iwakuma went seven innings, allowing three runs on seven hits. He walked one and struck out seven. He is now 5-0 with a 1.49 ERA in six appearances against the Angels. Last season, he was the only pitcher to pick up four victories over the Angels.
"He gets out of jams when he needs to," Howie Kendrick said. "Last year we were surprised when we see him coming out of the pen for these guys. Once he started in the second half, he was getting a lot of guys out. The guy has great stuff."
Kendrick posed a threat in the second with a two-out double into the right-field corner. But Trumbo struck out and Callaspo bounced out to second.
The Mariners started with two in the second. With the infield shifted to the right, Justin Smoak bounced a one-out single through the wide left side. Michael Saunders followed with his sixth home run into the right-field seats.
That extended the Mariners club record of hitting at least one home run in 22 straight games. The big league record is 27 set by Texas in 2002.
In the fifth, Brad Miller opened with a single and Nick Franklin walked. Ibanez sent Miller home with a double to right and Franklin was held at third. That also ended Blanton's afternoon.
Michael Kohn took over with runners on second and third and no outs. He quickly quieted the Mariners, striking out Kendrys Morales, intentionally walking Kyle Seager, then striking out both Smoak and Saunders. He has stranded 19 of 22 inherited runners this season.
"Mike Kohn did an incredible job to keep us in the game," Angels manager Mike Scioscia said.
The Angels finished under .500 (44-49) at the All-Star break for the first time since 2006 (43-45).