SANTA CLARA — The 49ers have not lost a game this season, and on Monday night they get to celebrate that in front of the people who built the franchise.

San Francisco (5-0) hosts the Washington Commanders (1-3-1) at Levi’s Stadium in Week 6 of Monday Night Football, kickoff 5:15 p.m. on ESPN and ABC. The game doubles as the team’s 80th-anniversary celebration: 94 former players are expected back, former offensive lineman Derrick Deese will serve as honorary captain, and four-time Super Bowl champion linebacker Keena Turner — now a team vice president and senior advisor — will be inducted into the Edward J. DeBartolo Sr. 49ers Hall of Fame at halftime as its 34th member.

There is history on the field, too. The 49ers and Pittsburgh Steelers are tied for the most Monday Night Football wins in NFL history at 55. A victory gives San Francisco the record outright.

Purdy’s night to climb the leaderboard

Brock Purdy enters the game with the league’s best QBR through five weeks, at 85.5, and a career passer rating of 105.4. He needs just five more pass attempts to qualify for the NFL’s all-time passer-rating leaderboard — where that number would put him at No. 1 — and three touchdown passes to reach 100 for his career.

He will have to do it short-handed. Deebo Samuel has been ruled out with a hamstring injury and is expected to miss an extended stretch. Receivers Ricky Pearsall, Demarcus Robinson and Christian Kirk are also banged up, leaving Mike Evans — playing through rib and Achilles soreness — as the clear No. 1 target. Evans leads the team with 24 catches for 326 yards and three touchdowns, and his seven-catch, 113-yard day keyed last week’s 32-29 comeback win in Seattle.

That Seattle game was a warning as much as a win. The Seahawks held the 49ers to 269 yards, 14 first downs and 4.8 yards per play, sacked Purdy three times and forced three turnovers. San Francisco still found a way in the fourth quarter — which is what 5-0 teams do — but Kyle Shanahan’s offense, ranked third in the league in scoring, was not itself for long stretches.

Daniels is the problem Washington brings

Washington’s record looks soft, but its quarterback is not. Jayden Daniels, back from a second dislocation of his left elbow and cleared with no limitations, threw for 199 yards and ran for 103 yards and two touchdowns on eight carries in last week’s 27-27 overtime tie with the Giants. Against a 49ers defense missing linebacker Dre Greenlaw — his suspension was upheld this week — Daniels’ legs are the thing to watch.

Running back Bill Croskey-Merritt, who ripped off a 33-yard touchdown run last week, is dealing with a groin injury but could play. Defensive backs Trey Amos and Nick Cross practiced in full and could return to a Washington secondary that ranks 29th in points allowed and has repeatedly blown fourth-quarter leads.

The 49ers, by contrast, are giving up fewer than 18 points a game and rank fourth in scoring defense, even with pass rusher Nick Bosa sidelined. Shanahan indicated this week that Bosa could return against Washington.

The line and the call

San Francisco is favored by 7.5 points, with the total set at 50.5. Expect a clear, cool night in the low 50s with a 10-to-15-mph breeze — football weather.

Washington’s defense has not shown it can close games, and Purdy has shown he can. Daniels will make it uncomfortable for a half. The 49ers go to 6-0, take the Monday night record for themselves, and send 94 alumni home happy.

Commanders at 49ers, Monday, Oct. 19, 5:15 p.m. PT, Levi’s Stadium. TV: ESPN/ABC. Streaming: ESPN app, NFL+.