Crabtree signed a six-year contract early Wednesday after a drawn-out negotiation process that had some wondering whether the star wide receiver would ever show up this season.
"It's a lot of relief off my shoulders," Crabtree said when formally introduced at team headquarters.
Crabtree gets a six-year contract that can turn into a five-year deal if he lives up to his potential as the 10th pick in the 2009 draft, a source told ESPN.com's John Clayton.
According to the source, Crabtree has a couple of scenarios that could void the sixth year of his contract. If he goes to a Pro Bowl during his first four years, along with playing 80 percent of the offensive snaps during a separate season in which the 49ers reach the playoffs, the source said the contract voids to five years. Another provision would be going to a Pro Bowl in the first four years along with going to a second Pro Bowl in five years.
According to the source, the Crabtree contract is for six years and $32 million that could maximize to $40 million if he achieves every incentive in the deal. The guarantee in the contract is $17 million, but he is expected to make $19 million over the first three years and $23 million over the first four years. The five-year deal is worth $28 million, according to the source.
Crabtree headed out Wednesday for his first practice as the 49ers prepare for Sunday's home game against Atlanta.
"Everybody came to a reachable agreement and it happened," Crabtree said, sporting a red No. 15 practice jersey and charcoal gray sweats. "I'm just glad I'm past that part. I'm very humble right now, man, it's a very humbling experience. Just getting a chance to sit back and better myself as a person, as a player, as a teammate. ... I feel like going through that it made me look at the world in a different way, look at my teammates a different way. Hopefully it will work out for the best."
Singletary called it a "fair deal for both parties involved."
The former Texas Tech star was the only draft pick who hadn't signed; even rapper MC Hammer got involved to finally make it happen.
Crabtree could provide the game-breaking receiving threat the 49ers have been lacking, assuming he can quickly learn the offense after missing all of training camp. The 10th pick overall, he also sat out offseason minicamps and organized team activities while recovering from a foot injury, but was a regular presence at the team's training facility.
Crabtree and his agent, Eugene Parker, met with three top 49ers officials Tuesday to work through his contract impasse. Crabtree balked at a long-standing offer of approximately five years and $20 million, with a reported $16 million guaranteed. Instead, he sought money comparable to what higher draft picks received.
"We came out of the gate and put a solid offer on the table," 49ers general manager Scot McCloughan said, still unsure what Crabtree's side didn't like about it. "I'm curious to find out because it goes against the norm. Very seldom do you see this."
Jaguars top pick Eugene Monroe, taken eighth overall, signed a five-year, $25 million contract that includes $19 million guaranteed.
Crabtree shook hands throughout the locker room to greet his teammates.
"We accept Crabtree no matter what," tight end Vernon Davis said. "I think his play will speak for itself."
Singletary acknowledged last month the 49ers discussed changing their offer to Crabtree, and team president Jed York said in mid-September the team hoped for a face-to-face meeting with Crabtree. The 49ers received a call Sunday that Crabtree and Parker were en route to the area. That meeting finally happened Tuesday.
Crabtree and Parker were joined by York, vice president of football operations Paraag Marathe and McCloughan. Hammer, a friend of Parker and client Deion Sanders, also participated.
Singletary found out the deal was done when he woke up Wednesday morning.
"This is a great day for the 49ers," he said. "It showed the commitment in place in having Crabtree here. Obviously Michael missed a lot of time, a lot of valuable time, and has a lot of work to catch up."
Crabtree's contract can be voided after five years with two solid seasons. It's unclear when Crabtree will be ready after missing so much time, but San Francisco has a bye next week. It's conceivable he could make his debut in a limited role Oct. 25 at Houston.
"It's going to be a process," said Singletary, whose team leads the NFC West and at 3-1 is off to its best start since 2002. "Hopefully after the bye, Mike will be ready to go. Certainly it's going to start small, a small role here and there, figuring out ways to get him on the field."
The 49ers needed to sign Crabtree by Nov. 17 for him to remain eligible to play this season. There would have been a seven-week window before the 2010 draft to trade Crabtree if he did not sign.
In August, a report surfaced that Crabtree was prepared to sit out the season, re-enter the draft in 2010 and wait for a hefty paycheck.
"I know there's been a lot of things said back and forth," Singletary said. "I've always said from day one, until I've heard something from Michael, all the other stuff doesn't mean anything to me. I'm very excited to have Mike Crabtree be part of this team. In my mind he has been since the day of the draft. Today really makes it official."
Crabtree caught 97 passes for 1,165 yards and scored 19 touchdowns last year, his sophomore season at Texas Tech. He finished his college career with 231 receptions for 3,127 yards and 41 touchdowns.
Information from The Associated Press was used in this report.