The Rams' offense is 31st in the NFL with just 308.0 yards per game. Their passing game is ranked 25th with 225.4 yards per game, increasing in recent weeks because of Los Angeles' profound struggles running the ball.
Fisher had finally seen enough on the field — and from Goff in practice — to warrant the inevitable change.
Goff will make his NFL debut Sunday when the No. 1 pick faces the Miami Dolphins as the Rams' starting quarterback.
Veteran Case Keenum has started every game, passing for 2,169 yards with 11 interceptions and nine TDs.

After weeks of increasing scrutiny on the offense's struggles, Fisher finally decided to see what they've got in Goff. Los Angeles couldn't score a touchdown in last weekend's 9-6 victory over the New York Jets,Jerseys NFL Cheap, failing to reach the end zone for the third time in nine games.
"It wasn't a spontaneous decision," Fisher said. "It was a progression. It's a gut feel. It's not an easy thing. It takes time, and we gave it time, and it was the right decision. We're looking forward to watching him play. ... He's going to have some moments, like all young quarterbacks do,Jerseys NFL Cheap, but he's going to do well."
"I think it's time," Goff said after practice Tuesday. "I'm ready to move forward and play. I'm just going to work hard and hopefully win."
Goff will get his first shot against the Dolphins, who have the NFL's ninth-ranked passing defense with potent pass-rushers Ndamukong Suh and Cameron Wake, who have combined for 12 sacks.
But after Goff didn't beat out Keenum for the job in the preseason, Fisher repeatedly declined to promote the rookie over the past two months even while his offense struggled on almost a weekly basis, saying he wanted Goff to be in an ideal position to succeed.
Los Angeles traded several high draft picks to Tennessee in April to move up to draft Goff, hoping to solve years of underperformance at the NFL's most important position. The Rams also traded up to make a splash in their return to Los Angeles after a 21-year sojourn in St. Louis, where they hadn't made the playoffs since 2004 or had a winning record since 2003.
It's increasingly clear that the Rams' offense doesn't provide an optimal opportunity for any quarterback, but at least Goff will now be learning on the job.
Goff will debut in front of his home fans at the Coliseum, where Rams fans frustrated by a dismal offensive season chanted "We want Goff!" two weeks ago during a loss to Carolina.
The Coliseum crowd has been eager for a change, booing the offense and chanting for the rookie while the Rams struggled through a 13-10 loss to Carolina two weeks ago. Los Angeles couldn't score against the Panthers until midway through the fourth quarter.
"It feels like a long time since I've got out there and played," Goff said. "I'm excited to get back out there. ... I saw a lot of stuff from the sidelines, as much as you can see during games, and learned from a lot of the things Case did,China Jerseys, good and bad. It's been a long process, I guess, trying to pick up everything and get ready for it. I think I have, and I think I've been ready for a little while. I feel good, and I feel excited."
Goff is the first quarterback chosen with the top pick who didn't start his team's opener since JaMarcus Russell in 2007. Since then, Matt Stafford, Sam Bradford,NFL Jerseys Clearance, Cam Newton, Andrew Luck and Jameis Winston had all started their teams' first games.
Goff watched the first nine games of his rookie season on the sideline for the Rams, who have scored an NFL-worst 15.4 points per game with one of the league's least productive offenses.
"We're expecting him to play well and win games for us, so it's an exciting time for us," Rams coach Jeff Fisher said.
Goff, who turned 22 last month, was a three-year starter at California in a spread offense bearing little resemblance to the Rams' more pro-style schemes. That additional learning curve persuaded the Rams to be patient, but Keenum has struggled along with the Los Angeles offense, repeatedly failing to make big plays in important situations.
The Rams then failed to reach the end zone against the Jets, but the defense carried them to their first win since early October.
The veteran has thrown eight interceptions and five TD passes over the past five games for the Rams,Nike Air Max 97 Silver Bullet, who endured a four-game skid before last weekend's win.
THOUSAND OAKS, Calif. (AP) — Jared Goff is ready to show the Los Angeles Rams he was worth the wait.