Sheets' counterpart, Yankees righty Javier Vazquez, suffocated the A's lineup and New York won the opener of a three-game set, 3-1.
Sheets finished a season-high 7 1/3 innings on Monday, allowing three runs on eight hits, but he lost for the fifth time in seven starts. He has now given up at least three earned runs in each of his past eight outings.
But for the 31-year-old Sheets, who missed all of last season, Monday's start was the latest example of the right-hander showing the ability to pitch deep into the games. Sheets has now completed at least six innings in each of his past 12 starts.
"I knew getting deep would be a process," Sheets said. "But I didn't realize it would be this difficult. I'm starting to feel better toward the end of games, which is good. I think my stuff is starting to get better, as opposed to earlier in the year, when it was decreasing a lot."
In fact, A's catcher Kurt Suzuki said Sheets' final pitch -- a 94-mph two-seam fastball that painted the outside corner to strike out Mark Teixeira -- was also his finest pitch of the evening.
"To know I can make that pitch at [the 109-pitch mark] -- it lets me know that my stamina is starting to build up," Sheets said.
With the July 31 non-waiver Trade Deadline looming, Sheets' name continues to come up in trade rumors. However, the nine-year vet said he spends no time worrying about speculation. As a player who has never been traded, Sheets said he expects to be with the A's through the end of this season.
"I'm an Oakland Athletic and that's who I'm pitching for, and that's who I try to win for," Sheets said. "I don't think it crosses any athlete's mind when you're out there. ... I realize the business of it, but it's not something I think you worry about."
Sheets had three 1-2-3 innings and didn't walk a batter on Monday, but on a night when Vazquez was dealing, the A's lineup fell short.
Oakland managed just three hits and two walks against Vazquez over seven innings, its only run coming via a Coco Crisp sacrifice fly in the third. The A's fared even worse against Joba Chamberlain in the eighth and Mariano Rivera in the ninth, as the final 13 Oakland batters were retired in order.
"[Vazquez] really didn't leave many balls over the plate," Suzuki said. "He was changing his speeds, hitting his spots and he was pretty good tonight. It was kind of a night where you tip your hat."
Oakland manager Bob Geren said that Vazquez was able to keep the A's off balance by throwing effective offspeed pitches in fastball counts.
It didn't hurt Vazquez to have a stellar defense behind him, either. Whether it was Derek Jeter's graceful, twirling putout of Mark Ellis in the third, Alex Rodriguez's diving stab and strike across the diamond in the sixth or Curtis Granderson and Colin Curtis' consecutive diving grabs to cap off the seventh, there was plenty of quality glove work on display Monday.
"When you think of [the Yankees], you think of other things," Geren said. "But their defense is solid also. They have a pretty balanced team all the way around."
Nick Swisher, who played for the A's from 2004-07, went 2-for-4 in his most recent return to Oakland Coliseum. He doubled off Sheets with two outs in the second before scoring the game's first run on a Granderson triple. Yankees catcher Francisco Cervelli then singled in Granderson to give the Yankees a 2-0 lead. Teixeira made it 3-1 Yankees with his no-doubt solo shot off Sheets in the sixth.
"Two runs with two outs was big," Teixeira said. "Sheets pitched very well tonight, and it wasn't going to be a high-scoring night with the way those guys were pitching. It was good to get three off him."
The A's entered Monday's contest with a bit of momentum, having won seven of nine games -- albeit against three last-place teams -- but they couldn't take advantage on a night when both the Angels and Rangers lost big.
The A's now sit eight games behind the Rangers for first place in the American League West.
Though it came in a losing effort, A's third baseman Kevin Kouzmanoff snapped his career-long 0-for-30 streak with a fourth-inning single. Reliever Michael Wuertz also finished off the eighth inning without a blemish and hasn't allowed a run over his past eight appearances, a span of 6 1/3 innings.
Alex Espinoza is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.