Not many teams can lose their leading rusher and two of their top three wide receivers, and say with a straight face that they’re looking for improvement next season on offense. But that’s where the Rams stand after losing running back Steven Jackson (to Atlanta) and wide receivers Danny Amendola (New England) and Brandon Gibson (Miami) in free agency. With the “garage sale” phase of free agency about to start and the draft still to come, it’s safe to say the St. Louis offense will undergo a massive makeover for 2013. This was partly by design and partly because of outside circumstances. At the NFC coaches’ breakfast Wednesday, Jeff Fisher said he knew it was possible that Jackson, Amendola and Gibson could all land elsewhere in free agency. “We’ve known obviously since September about ‘Jack’s’ future,” Fisher said, referring to the change in Jackson’s contract made at that time, allowing him to void the final year of his contract. “It was a good situation for both sides.” As for Amendola, Fisher said Wednesday the Rams got a strong hint from Amendola’s agents about where things might be headed in September as well. “We made an attempt to (negotiate with) Danny in September and they decided to wait,” Fisher said. “They had made their mind up that they were gonna wait — just wait till free agency. “Our issue with Danny was — we didn’t want to lose Danny; we were willing to pay Danny — but Danny had missed a lot of games. So our preference was as we were going through this, is he needed to be on the field to get paid, which makes sense. They understood that, and we understood that. You know, it just didn’t work out. But he’ll do well and we’ll have options.” When it comes to those “options” at wide receiver and also at running back, Fisher was speaking specifically of the Rams’ draft class of 2012. Namely, wideouts Chris Givens and Brian Quick, and running backs Daryl Richardson and Isaiah Pead. “We’ve always said that players make their biggest improvement from year one to year two,” Fisher said. And it begins with the offseason conditioning program, which for the Rams starts April 15.