On a night when rookie catcher Adam Moore became the franchise-record 22nd player to hit a home run this season, and Ken Griffey Jr. slugged his 629th career home run during a four-run first inning, the spotlight fell on Morrow.
The only hit he allowed was an infield single to Rajai Davis in the fourth inning. The only other Athletics to reach base against him drew back-to-back two-out walks in the eighth inning.
"I was running out of gas, and the battle with [Eric] Patterson kind of took something out of me," Morrow said. "I could feel my legs going a little bit and I was just rushing the ball up there. I settled down after the first couple of pitches and got the [third] out."
The Mariners (82-76) gave Morrow plenty of early run-support against Athletics starter Clayton Mortensen, a Gonzaga University product. A four-run getaway, highlighted by Griffey's three-run blast over the center-field fence, was followed by a two-run rally in the second inning.
It was smooth sailing after that for Morrow, who began the season as the Mariners' closer, lost that position and was sent back to Triple-A Tacoma to relearn the art of starting.
He had mixed results in the Minors, but returned on Sept. 9 and took his place in the rotation.
Morrow gradually improved and was especially impressive in his start against the Rays on the most recent road trip, when he pitched five stellar innings before losing his command.
He was rock-solid until there were two outs in the eighth on Wednesday night.
"I don't know if we've had a better-pitched start this year," manager Don Wakamatsu said. "You can put that right up there with any of the top ones. It's awfully nice to see the adjustments in a guy, especially having his last start end on a note like that and give us a lot of hope going into next year for him.
"I saw a lot of movement on his fastball. I saw him change speeds, and until the eighth inning, he hadn't walked a batter. His tempo to the plate was excellent. It really was a clinic."
It was the kind of outing that could make the organization decide that Morrow definitely should be in the rotation next season.
"I don't know if you can ask for any more in the last appearance of the year," Wakamatsu said. "Going into Spring Training, when we're looking for spots in the rotation, for him to end on that gives us a strong belief system going into the winter."
Morrow believes he proved something.
"I hope at least we can look and see I'm moving in the right direction," he said. "Almost exponentially, start to start, it's getting better. There's obviously some consistency things I need to work on, and that's going to come from repetition. But I hope I've definitely gone the right direction."
The clinic Morrow put on against the American League West rivals was visible from both dugouts.
"Everything he threw was around the plate, and when he fell behind, he made great pitches," Athletics first baseman Daric Barton said. "He moved his pitches around, in and out, and threw a heck of a game."
Moore, who caught the majority of Morrow's starts in Tacoma, said it was one of the best pitching performances he had ever been involved in.
"Even talking to him in the dugout, he was relaxed and having a good time," Moore said. "That was the Brandon I caught a lot in Tacoma, and hopefully tonight he builds that up to be successful at this level. He has some of the best stuff I have ever caught.
"I was able to throw down a curveball, slider or fastball when he needed it. His command was tremendous tonight. He was just lights-out."
And Moore caught just six of Morrow's eight innings.
Kenji Johjima started the game at catcher, but was hit in his left elbow with a pitch in the first inning and had to leave the game in the second.
Moore came in, guided Morrow through the Athletics lineup and contributed an opposite-field home run in the fourth inning.
He became the 22nd Mariners player to hit a home run this season, breaking a franchise record previously shared by the 1983 and '98 teams.
Griffey was on that '98 team.
He hit 56 home runs that season. The one he hit on Wednesday night was his 18th and the second in two nights.
Mortensen became the 407th hurler to surrender a home run to the 13-time All-Star and Junior has now welcomed 16 pitchers into his home run club this season.
But even Griffey was caught up in the Morrow gem.
"This being his last start of the year, to go out the way he did, is nice," he said. "It was fun to watch."
His record is only 2-4 this season, but even so, Morrow said,"It's a good end to the season."