"I'd never thought I'd be on [the] other side of the rivalry," Youkilis said.
Youkilis is receiving a $12 million, one-year contract. Rodriguez is out until at least June and maybe longer after he undergoes a second hip surgery in January.
"He will be penciled in as our every-day third baseman until Alex comes back," Yankees general manager Brian Cashman said. "He certainly cushions the blow of losing Alex. That's a difficult loss. When you have a healthy Alex Rodriguez you have a really, one of the more productive players, but I'll be honest, I couldn't think of anyone better to replace him in the short-term than Kevin Youkilis. He's a gamer and competitor that gives you a chance to win and is hungry and has a desire to win."
Youkilis said he was surprised by the Yankees' interest in him. But after weighing offers from the Cleveland Indians and looking at some "West Coast options that didn't go through" -- one believed to be the Los Angeles Dodgers -- Youkilis decided that the Bronx would be his choice.
Before agreeing to play for the Yankees, Youkilis reached out to former teammate Johnny Damon to find out what the New York experience would be like.
"It's a great thing to put on the pinstripes," Youkilis said Damon told him.
Youkilis said he can't control how Yankees fans who once had disdain for him will react now that he's on their side, but he noted that chants of "Youk" and booing sound very similar.
"Over the years, I've had a lot of Yankee fans come up to me and say, "I love the way you play the game,' " Youkilis said.
Youkilis, who will turn 34 in March, hit .235 with 19 homers and 60 RBIs in 111 games with the Red Sox and the Chicago White Sox last season. If Rodriguez, 37, were to come back and be able to play third, Youkilis could see time spelling Mark Teixeira at first and as a designated hitter.
The Yankees next are expected to announce a new deal for Ichiro Suzuki. The team and the outfielder were closing in on a contract that will pay him between $12 million and $13 million for two seasons. When the contract is signed, it will be the first multiyear deal that the Yankees have agreed to this offseason. The deal will take Ichiro until his 41st birthday.
The Yankees are not pursuing their former right fielder, Nick Swisher. Ichiro is expected to man right field, with Brett Gardner in left and Curtis Granderson in center. The Yankees have discussed switching the faster Gardner to center and Granderson to left.
Yankees owner Hal Steinbrenner has mandated that payroll be cut to less than $189 million for the 2014 season to take advantage of the luxury tax and revenue sharing provided by the new collective bargaining agreement. Besides Youkilis, the Yankees have signed Mariano Rivera, Andy Pettitte and Hiroki Kuroda to one-year contracts for a combined $49 million for 2013.
He is expected to be asked about his relationship with reliever Joba Chamberlain, who once was suspended for two games for throwing at Youkilis. Chamberlain also hit Youkilis last season when Youkilis was with the White Sox, though there was no fallout.
"Joba has zero ill will toward him," Chamberlain's agent, Jim Murray, said earlier this week.
Youkilis said there will be no problems for him with Chamberlain, who left Youkilis a voicemail after the news broke earlier in the week that he had agreed to join the Yankees. The two have not spoken yet.
"It is not a big deal to me," Youkilis said. "If it was that big a deal, I wouldn't have been signing with the Yankees. But I don't think it is that big of a deal. A lot of it is made out within the media and the fans."
Said Cashman: "I definitely don't believe there is an issue with him coming to New York. I think it's an easier transition for someone like that after he's been traded. He's not going from Boston to New York. He's basically going from Boston to Chicago to New York. I think in the end he chose us for a reason, because it was the best opportunity for him to play and compete."
Information from ESPNNewYork.com's Wallace Matthews was included in this report.