SEATTLE — A blend of green mixed in with the sea of blue-clad Mariners’ fans in the lower bowl of Safeco Field.

The back-and-forth chants between the Seattle and Oakland faithful were audible throughout the stadium.

And, in less than a week with his new team, right-handed pitcher Jason Hammel took notice.

Hammel, a 2000 South Kitsap graduate, left the last-place Chicago Cubs for the team with the best record in baseball at the all-star break in one of baseball’s biggest trades in recent years. The Cubs sent Hammel and Jeff Samardzija, who was selected to the National League All-Star team, to the Athletics for one of the game’s top prospects, shortstop Addison Russell, and two other players on July 5.

For Hammel, a nine-year major-league veteran, the scene last weekend at Safeco was reminiscent of earlier in his career when he was a member of a burgeoning Tampa Bay team. In 2008, the Rays — a perennial loser in their first decade of existence — emerged to win the American League East Division over traditional powers New York and Boston.

The script is a little different as the Athletics seek their third consecutive American League West title and have four championships since moving in 1968 to Oakland. But there are other similarities. Despite having a 59-36 record, the Athletics hold a slim lead over the Los Angeles Angels (57-37), who have the second-best record in baseball. And third-place Seattle (51-44) would qualify for the playoffs if the season ended now.

“It’s fun being part of this division,” Hammel said. “It’s almost like the AL East, where it was such a powerhouse for such a long time. Now you can see age taking its factor in the AL East and you come over here and it’s a bunch of young guys and solid teams performing well.

“It’s a playoff-type atmosphere everywhere we go here.”

One that some thought Hammel would enjoy near the shores of Puget Sound. On June 14, the Chicago Sun-Times reported that sources expected Hammel to be traded to the Mariners. That would have enabled him to pitch for the team that drafted him in the 23rd round in 2000.

“I never really listen to the rumors until something actually does happen,” Hammel said. “I had no say in the matter.”

What happened next stunned many baseball analysts. Some thought Oakland, which entered the all-star break with the best ERA (3.12) in the American League, would not attempt to upgrade its pitching staff. Hammel said the trade surprised him for a couple of reasons.

“I knew the possibility of us being traded was very high, but us getting traded together was very slim,” he said. “The Oakland A’s are not a team that usually makes blockbuster deals. For them to scoop up both of us makes the transition easier because we know each other and it says a lot about the organization they have here — they’re trying to win.”

It marked the third time in his career that Hammel, who has been thrust into a variety of situations, was traded. The first time, when the Rays traded him in 2009 to Colorado for minor-league pitcher Aneury Rodriguez, Hammel entered perhaps the worst pitching environment in the major leagues at Coors Field, where home-run rates annually are among baseball’s highest.

But it also enabled Hammel to become a full-time starter for the first time. And once he was traded in 2012 to Baltimore — a much more conducive environment for pitchers — he flourished. That season he posted a career-best strikeout ratio of 8.6 per nine innings. That translated into an 8-6 record and a 3.43 ERA.

It also was success he could not sustain. Hammel underwent surgery to remove to remove floating cartilage in his right knee in July 2012 and did not pitch the rest of that season. Upon his return last year, Hammel’s strikeout ratio fell to pedestrian levels (6.2) and his ERA swelled to 4.97.

In an effort to rebuild his value, Hammel settled for a one-year, $6 million contract with the Cubs. At the time of the trade, Hammel’s strikeout ratio returned to its 2012 levels and his ERA (2.98) was a career-best mark. Hammel said his success is simple to explain.

“That’s basically it — I’m healthy,” he said. “Now that I’m healthy, you can see and I can see what I can do. It’s nice to get back to what I was doing in ’12.”

Hammel, who had an 8-5 record with the Cubs, also should have little difficulty setting his career high in wins. He won 10 games for the Rockies in both 2009 and ’10. In his first start July 9 against San Francisco, he allowed two runs in five innings in a 5-2 loss.

“We look for the quality outings we’ve seen from him in Chicago,” Oakland manager Bob Melvin said. “We’re awfully excited about having him. He’s one of the quality pitchers in all of baseball. We’re really lucky to have him.”

Melvin noted that Hammel quickly has assimilated in the clubhouse. Hammel, who lounged on one of the oversized couches with teammates in the visitors clubhouse before Saturday’s game, agreed.

“You definitely feel no tension in here,” he said. “Everyone is pulling in the same direction.”

One that brought Hammel to a veteran-laden club in search of the franchise’s first championship since 1989.

“The younger teams are still trying to figure out how to be professional, perform at the level they need to and stay there,” he said. “Coming over here, there’s guys who want to win and expect to win.”