Gore was welcomed back by a new coaching staff and several players who have been anticipating his arrival.
"I almost hugged him and gave him a kiss, but I tried to play it cool," wide receiver Josh Morgan said. "It was really exciting to see him."
Gore, who missed San Francisco's final five games last season with a fractured hip, is in the final year of his contract with the 49ers that will pay him $2.9 million this season with a $2 million roster bonus. He is seeking a contract extension.
Gore said the holdout was a mutual decision between him and agent Drew Rosenhaus. But a few days away from the team was all it took to convince Gore to return.
"I love the game and I missed the game," Gore said. "I'm a football player and I missed being out here with my team. I'm here to get better and try to take this organization where it needs to go."
Gore has led the 49ers in rushing every year since being drafted in 2005, including a team-record four consecutive 1,000-yard seasons from 2006-2009. Gore was on his way to extending that string last season before his injury. He finished the season with 853 yards rushing and 46 receptions for 452 yards.
The 49ers are installing a new offense this summer under new coach Jim Harbaugh, and Gore once again figures to be a key component of San Francisco's attack. Harbaugh wasted no time giving Gore extensive duty with the first-team offense during his first day back.
"There's quite a difference in communication when he's in the huddle," Harbaugh said. "I'm very impressed with the way he hits the hole extremely quick and fast. It raises the competition and gives some of our young backs an example of what a top-notch pro looks like."
Smith and other free agents who recently signed contracts with the team can't practice until Thursday, and Crabtree has a foot injury that could keep him out several weeks.
Gore spent the offseason working out near his home in Miami and did not participate in player-organized 49ers workouts in June that were attended by most of his offensive teammates at San Jose State University.
The entire offensive tempo seemed to pick up with Gore back on the field.
"Frank's a leader on this football team and the energy is up," tackle Joe Staley said. "Any time Frank's back there, he's going to take care of business. Just having him back on the field, his presence, is good for everybody and it raises spirits. The way he prepares and the way he communicates is a standard to live up to."
Harbaugh said "diligent" contract negotiations continue with Gore's representatives and he expects there to be a resolution on a new deal "sooner rather than later."
"Frank's a 49er and we want Frank here," Harbaugh said. "We want Frank happy, too."
Said Gore: "I want to be a 49er forever, and if the contract comes, it comes. I felt like a kid out there today, and I'm just happy to be back. I'm sorry about the little holdup, but I'm back and I'm ready to go to work and get better."
Copyright 2011 by The Associated Press