SEATTLE -- Michael Pineda spent his first season of major league baseball learning under the tutelage of Seattle Mariners ace pitcher Felix Hernandez.

On Monday night, in Pineda's first return to Safeco Field, the New York Yankees starter taught Hernandez a thing or two.

The New York Yankees' 26-year-old starting pitcher out-dueled his former teammate on the way to a 7-2 win over the Seattle Mariners.

"I was very excited today for this game. I was very happy to be here and pitching in Safeco Field. I'm happy tonight," Pineda told reporters after the win. "I had really good focus today and tried to do my best on the mound."

Pineda (7-2) allowed two earned runs over six innings, while Hernandez turned in his worst start of the season and one of the most forgettable of his 10-year career. The 29-year-old Hernandez (8-2) allowed season highs of seven earned runs and five walks in 4 2/3 innings.

Hernandez opened the game with three perfect innings before struggling with his command and the dirt on the pitcher's mound in the fourth. The veteran continually kicked at the dirt and tried to remove it from his cleats as the game started to unravel.

Afterward, Hernandez told reporters the mound wasn't much of a factor in his performance, and manager Lloyd McClendon echoed those sentiments.

"He just didn't pitch well," McClendon said. "He's human. "I'm not going to sit here and make excuses and say the mound was the reason. He just didn't pitch well."

Pineda, meanwhile, was nearly flawless for six innings before the Mariners finally got to him in the seventh. A Mark Teixeira grand slam in the fifth inning had helped give Pineda a 7-0 lead, and he had nine strikeouts and just four hits allowed over six scoreless innings before Seattle opened the seventh with three consecutive hits.

The Yankees (27-25) had just seven hits but got plenty of offense, thanks to Teixeira's grand slam, a wild pitch and five walks.

Teixeira's homer did the most damage, giving the Yankees a 7-0 lead before Hernandez could get the second out of the inning.

"It felt big," Teixeira said of the home run. "The way Michael was pitching, we didn't know how many we'd need. But anytime you can score seven off Felix Hernandez, we'll take it. It doesn't happen often."

Seattle (24-27) lost its third game in a row and could match its longest losing streak of the season if the Yankees win on Tuesday night. McClendon shook up his batting order before the game, but Seattle didn't get a single runner past first base until the seventh inning.

Hernandez retired the first nine batters before running into trouble in the fourth.

After giving up back-to-back singles to center fielder Brett Gardner and third baseman Chase Headley to lead off the inning, Hernandez threw a wild pitch that got past catcher Mike Zunino and brought in Gardner from third base for the first run of the game. Hernandez then walked the next two batters before Headley scored on a bases-loaded double play for a 2-0 New York lead.

The Yankees had two hits and three walks in the fourth, yet scored both runs without the benefit of an RBI.

Things got even worse for Hernandez in the fifth. Two walks and a single loaded the bases before he finally got an out -- on a Headley sacrifice fly that increased the Yankees' lead to 3-0. Designated hitter Alex Rodriguez loaded the bases again with a single before Teixeira stepped in and delivered his ninth career grand slam, and his 15th home run of the year, on a 2-0 pitch. Right fielder Carlos Beltran's double two batters later ended Hernandez's night after 85 pitches.

The five walks and seven earned runs were season highs for Hernandez, who went into the game ranked third in the American League with a 1.95 ERA. By the time the book was closed on him after Monday's fifth inning, his season ERA had risen to 2