The duo formed an impressive partnership at the heart of the Reds' back line last season, meaning that Carragher often spent long spells on the substitutes' bench.
|5/4||Liverpool are 5/4 with William Hill to be the only team to score when they face Hearts on Thursday
"It's probably not so good for me but, joking apart, it's absolutely vital we keep them," the 34-year-old told the Daily Star.
"I know Vincent Kompany was great for Manchester City last season but, for me, as a defensive partnership these two are the best in the Premier League.
"I don't think either has signed a new contract just yet but Martin is very close and Daniel wants to stay at Liverpool. That's brilliant news."
Carragher looks set to win back his place in the Liverpool defence after Agger conceded a penalty and received a red card in his side's 3-0 opening-day defeat at West Brom on Saturday.
His partner Skrtel also gave away a spot kick in new boss Brendan Rodgers' disappointing first league game in charge of the Reds at the Hawthorns.