BALTIMORE – The Yankees were on the best roll of their season, winning seven straight to pull one-half game ahead of the Red Sox in the AL East when they reported to Camden Yards yesterday.

Yet, Joe Torre saw something he couldn’t ignore in Wednesday’s 4-3 win over the Orioles. So, prior to last night’s game, Torre held a six-minute meeting with his club to remind it that little things matter. Shane Spencer was Exhibit A because his throw to the wrong base Wednesday allowed the potential tying run to move into scoring position in the eighth inning.

“We just had a little housekeeping to do, that’s all,” Torre said of the meeting. “It was nothing serious. I mean it’s serious, but nothing dramatic. Throwing to the wrong base.”

With runners on first and third, Spencer caught Jeff Conine’s fly in right field and foolishly attempted to throw out Jerry Hairston out at the plate. When Spencer’s throw was too high to be cut off, pinch-runner Brady Anderson moved from first to second. Mariano Rivera took Spencer off the hook by fanning Jay Gibbons.

Columbus right-hander Adrian Hernandez was put on the DL yesterday with a slight sprain of his left knee. The move allowed the Clippers (Triple-A) to add catcher Bobby Estalella to the roster. Estalella was acquired from the Giants with minor league right-hander Joe Smith for Brian Boehringer Wednesday.

Asked if Estalella, a muscular right-handed hitter who had 14 homers last year for the Giants, was acquired with an eye on helping the major league club this year, Cashman said, “I wouldn’t rule it out, that remains to be seen. Two years ago he was the Phillies’ No. 1 prospect. At the least, he is insurance. At the best, he helps us here. He was the Giants’ starting catcher out of spring training.”

LHP Andy Pettitte (8-4; 2.95 ERA) opens the Subway Series tonight at Yankee Stadium against LHP Al Leiter (4-7; 3.74). RHP Mike Mussina (9-7; 3.55) draws RHP Kevin Appier (5-8; 4.15) tomorrow and LHP Randy Keisler (1-2; 7.45) faces RHP Rick Reed (7-4; 3.10) Sunday night.