By The Associated Press

The short summer vacation is over for NFL players. It’s time to begin the journey to Super Bowl 59.

Coming off a disappointing finish in the AFC championship game, the Baltimore Ravens became the first team to open training camp when they welcomed rookies on Saturday. Nineteen more teams get underway this week and all 32 clubs will open doors by July 24.

Everyone is 0-0 but expectations aren’t the same. Some teams are legitimate contenders. A few are rebuilding.

Patrick Mahomes and the Kansas City Chiefs are aiming to become the first team to three-peat since the 1965-67 Green Bay Packers won three consecutive NFL championships.

Eight teams have new head coaches. Several star quarterbacks changed teams.

Training camp dates

While 20 teams begin camp this week for rookies, most veterans don’t report until next week. Only the Ravens, Chiefs, Chicago Bears and Houston Texans will have their full teams in camp this week. The defending AFC South champion Texans are first to open doors to vets on Wednesday.

The Texans and Bears will kick off the exhibition season in the Hall of Fame game on Aug. 1 in Canton, Ohio.

The Chiefs will host the Ravens in a rematch of the AFC title game to start the regular season on Sept. 5.

New head coaches

Jim Harbaugh is back in the NFL with the Los Angeles Chargers after leading Michigan to a national championship. Dan Quinn took over for the Washington Commanders, getting his second head coach opportunity. Raheem Morris also is a second-time head coach, taking the job with the Atlanta Falcons.

Dave Canales (Carolina Panthers), Mike Macdonald (Seattle Seahawks) and Brian Callahan (Tennessee Titans) are first-timers after successful stints as coordinators.

Antonio Pierce was promoted from interim coach in Las Vegas after leading the Raiders to a 5-4 record in the second half of last season.

Jerod Mayo has the biggest shoes to fill, replacing six-time Super Bowl champion Bill Belichick with the New England Patriots.

Teams with new QBs

Kirk Cousins joined the Falcons in one of the early surprises in free agency. Atlanta then pulled off a bigger shocker, selecting QB Michael Penix with the No. 8 pick in the draft after giving Cousins $100 million guaranteed.

Russell Wilson tries to revive his career in Pittsburgh where he’ll enter camp as the starter but the Steelers also acquired Justin Fields just in case.

The Bears drafted Caleb Williams at No. 1 overall and the Commanders took Heisman Trophy winner Jayden Daniels second. Both are likely starting Week 1. The Patriots selected Drake Maye third, but he could start the season backing up veteran Jacoby Brissett.

Sam Darnold replaces Cousins in Minnesota only to keep the seat warm for rookie J.J. McCarthy.

Veteran Gardner Minshew will compete with second-year pro Aidan O’Connell for the starting spot in Las Vegas.

Rookie Bo Nix will battle Jarrett Stidham for the job in Denver. The Broncos also added Zach Wilson.

Top camp storylines

Keep an eye on potential holdouts.

Cowboys All-Pro wide receiver CeeDee Lamb missed mandatory minicamp and may not report to camp because he wants a new contract. Several of Lamb’s peers got paid this offseason and he’s next.

Justin Jefferson set the market for elite receivers, getting a four-year, $140 million contract extension that included $110 million in guaranteed money. A.J. Brown, Amon-Ra St. Brown, Jaylen Waddle and DeVonta Smith also received new deals.

The Cowboys could have salary cap issues. QB Dak Prescott enters the final season of a four-year, $160 million contract and star edge rusher Micah Parsons is due for a new deal soon.

Lamb isn’t the only receiver looking for more money. San Francisco’s Brandon Aiyuk and Cincinnati’s Ja’Marr Chase are potential holdouts or hold-ins — those are players who show up to avoid fines but don’t practice.

Edge rusher Haason Reddick was traded from Philadelphia to the Jets because he wants a new contract. New York didn’t give him one so he didn’t report for offseason workouts.

The Dolphins and QB Tua Tagovailoa are talking about a new contract as he enters the season on the final year of his rookie deal.

It’ll be interesting to see how Tagovailoa handles the preseason if negotiations stall. His teammate, Tyreek Hill, has already stated he wants a revamped deal after losing his status as the highest-paid wideout.

Other camp storylines

Aaron Rodgers is returning to the New York Jets after his first season with the team lasted just four plays because of a torn Achilles tendon.

Rodgers, who skipped mandatory minicamp but attended OTAs, has been throwing since the end of last season and should be ready to go.

Cousins is also returning from a torn Achilles tendon. He participated in Atlanta’s offseason sessions and will navigate an odd situation with his future successor already on the team.

The NFL dramatically overhauled the kickoff rules so the preseason will be the first opportunity to see how teams will handle all the changes.

Roster cuts

Teams can carry a maximum of 90 players throughout training camp and for all of their preseason games. Rosters must be trimmed to 53 by 4 p.m. EDT on Aug. 27.

Camp hot spot

California will host six teams for training camp, including the three teams (Rams, Chargers, 49ers) that will play in the state. The Cowboys, Saints and Raiders also will hold camp in the Golden State.