New York (70-48) at Boston (69-50)

The New York Yankees knew they would be entering their critical five-game series with the Boston Red Sox at Fenway Park with a very precarious lead in the AL East. Thanks to an alarmingly poor series against one of the league’s worst teams, that lead might not last into the weekend.

The Yankees (70-48) limp into Fenway Park on Friday for a day-night doubleheader, opening a series that could go a long way toward determining the division champion.

New York’s lead over Boston in the East reached three games Monday with a victory over lowly Baltimore, owner of the AL’s third-worst record, and the Yankees thought they might have a chance to roll into Fenway with an even larger lead. Instead, the Orioles took the last two games of the series, 3-2 on Wednesday night and 12-2 on Thursday.

The stunningly poor performance left the Yankees only 1 1/2 games ahead of Boston (69-50), which avoided a three-game sweep by beating Detroit 6-4 on Wednesday to pick up one game, and was idle Thursday as New York lost.

“This game has nothing to do with tomorrow,” Yankees manager Joe Torre said. “We go up there. It will be the usual craziness.”

Now, both clubs gear up for a rare five-game set, the result of a May 2 rainout in their first series of the season. The usual fan and media frenzy is certain to surround the marathon showdown—something the players are doing their best to steer clear of.

“It seems like a cliche, but we gotta take it one game at a time—even the doubleheader,” Red Sox third baseman Mike Lowell said. “If you get caught up in what the five games might mean, you’re just adding distraction to something we have to be very focused on.”

What neither team will be able to avoid, though, is the poor state of their respective pitching. New York starter Jaret Wright lasted only three innings Wednesday, giving up five runs, and the two pitchers the Yankees have lined up for the doubleheader haven’t been much better of late.

New York will send Chien-Ming Wang (13-5, 3.84) to the mound in the opener. While the right-hander has been one of the team’s top starters this season, he has run into problems in his last two outings, going 0-1 with a 7.84 ERA. In his last start Sunday, he allowed a career-high 13 hits and five runs in 5 1-3 innings of a 5-2 loss to the Angels.

That followed a five-inning effort at Chicago on Aug. 8, when he gave up four runs and seven hits in New York’s 6-5 defeat. The short outings are uncharacteristic for Wang, who has pitched at least seven innings in 14 of 25 starts this season.

Wang is 1-2 with 4.91 ERA in five career games—four starts—against the Red Sox, and 0-2 with a 6.62 ERA at Fenway. He did, however, throw seven innings of one-run ball for a 2-1 victory June 6 in his last start against Boston.

Right-hander Sidney Ponson (4-5, 5.82 ERA) will come out of the bullpen and start the nightcap. Ponson, who briefly held the fifth starter’s spot after being picked up in mid-July, last pitched Friday, when he threw three innings of relief against Los Angeles. He gave up three runs and five hits in New York’s 7-4 defeat.

Ponson’s last start came July 23 at Toronto, where he allowed six runs in just 2 1-3 innings of a 13-5 loss.

He has struggled badly in his career against the Red Sox, going 3-10 with a 6.37 ERA in 18 starts. He went 1-1 with a 3.75 ERA in two starts against them last year while pitching for Baltimore.

Boston’s scheduled starters also have been shaky recently.

Jason Johnson (3-11, 6.26), loser of seven straight decisions, will make his sixth start for the Red Sox in the opener. He didn’t receive a decision in his last outing, giving up seven runs and nine hits in 5 1-3 innings of Boston’s 8-7 loss to the Orioles on Saturday.

The right-hander was pounded for six runs and 10 hits in 5 2-3 innings of a 6-1 loss to the Yankees on June 14 while pitching for Cleveland. He is 2-9 with a 6.03 ERA in 17 starts against New York.

Rookie Jon Lester (6-2, 4.09) will oppose Ponson in the second game. He won his last start Sunday, but gave up four runs and nine hits in five innings of an 11-9 victory over Baltimore. The left-hander, who has a 6.92 ERA in his last five starts, will be facing the Yankees for the first time.

“The way the Yankees chew up pitches, we might have to (keep 13 pitchers on the roster),” Boston manager Terry Francona said. “We have Lester and Johnson going. I hope both of them go nine (innings), but going into the game, you certainly have to be aware that they haven’t.”

If Boston has an advantage on the mound Friday, it may lie in a rested bullpen. Yankees manager Joe Torre had to use four relievers after Wright departed early Thursday, and New York’s bullpen has already been used extensively during the first 10 games of a 21-game, 20-day stretch.

Boston bolstered its lineup Thursday, acquiring Eric Hinske from Toronto for a player to be named. The left-handed hitting Hinske, who can play outfield, first base and third base, is hitting .264 with 12 home runs and 29 RBIs.

The Yankees and Red Sox have played four previous five-game series and each team won two, with a pair of sweeps and the other two ending in 4-1 results. The clubs, though, haven’t met in five straight games since 1973.

The Yankees and Red Sox have split 10 meetings this season.