The Rhinos were already looking to secure a replacement for stand-off Rob Lui, who is currently sidelined through injury and will leave the club at the end of the season, and Agar admits the loss of Eastmond, just two matches into his comeback, has highlighted a deficiency in his squad.
Agar said: “We will need to bring another spine player in, be that a full-back or half-back.
“This has clearly forced our hand even more. We’ve got Jack Walker out long-term and Rob Lui is retiring so it’s fair to say we’ll be playing Liam Sutcliffe in the halves all year.
“I don’t think there’s any need immediately to get in the market because, given what’s happened with Kyle, it’s really important for us that we don’t take another short-term route.
“Kyle was never meant to be short term but we don’t want to end up with a player that’s not going to be with us too long.
“Rob Lui’s fitness is hopefully around the corner which will help us for the rest of this season.”
Agar praised the bravery and honesty of dual-code England international Eastmond, who joined the club on a two-year contract on the eve of the season but struggled to regain the fitness he needed to compete at the highest level.
Agar said: “I think it was a really brave decision. When we signed Kyle, we knew there was some risk, for a guy that has been out of the game so long.
“We were prepared to support him all the way through it but there was a realisation that it was going to be a longer road back than we anticipated.
“For every two steps forward, there were probably three steps back in terms of getting him on the training field.
“When the fire is not burning as strongly as it should be, it’s a very difficult place to be and he was very honest. He needs to be applauded for that.
“We gave it a go but it wasn’t to be and the way it ended is a real credit to Kyle.”
Meanwhile, Agar’s squad will be boosted by the return from suspension of forward Zane Tetevano and utility back Richie Myler for Sunday night’s home game against Hull.
Tetevano was given a four-match ban for a high tackle in only his third appearance for the club, while Myler was suspended for two games for dissent.
Agar added: “To get Richie and Zane back gives us a lot of experience and quality in two important roles for us.”