The world champion Red Sox aren’t getting fat.

According to a person who knows Carlos Beltran, the switch-hitting right fielder has drawn strong interest from the Yankees’ blood rivals.

The person said the Yankees and Orioles are in on Beltran, too, but the Red Sox have been more aggressive.

Of course, it’s early in the process and that could change. Beltran, 37 in late April, is expected to turn down the Cardinals’ $14.1 million qualifying offer Monday. Teams signing him will forfeit a draft pick in June.

Monday is also the day the Yankees will learn whether Curtis Granderson accepts their qualifying offer. If he does it’s not likely the Yankees will have room for Beltran in an outfield that already houses Alfonso Soriano in left and Brett Gardner in center. If Granderson stays, he would play right field. Beltran is trending toward being a designated hitter, but he will command the type of money rarely given to a full-time DH not named David Ortiz.