For Stanford football, life without Bryce Love, JJ Arcega-Whiteside, Trent Irwin, Kaden Smith, Joey Alfieri and Bobby Okereke begins Tuesday with the start of spring practice.

The Cardinal are coming off a 9-4 season that included a 6-3 Pac-12 record (third place in the North) and ended with a Sun Bowl win over Pittsburgh. To the staff, the players and most fans, it was a disappointing year in view of the high expectations.

Fortunately for Stanford, quarterback K.J. Costello chose to return for his junior season in 2019 rather than enter the NFL draft.

The Cardinal still face many key questions as they prepare for one of the most difficult schedules in the country. Some won’t be answered until the end of training camp in August and possibly not until well into the regular season.

• Is Davis Mills ready to be the No. 2 quarterback?

Mills will be a redshirt sophomore this season. He was one of the most highly touted quarterbacks in the country coming out of high school in Georgia, but he has been plagued by knee problems on the Farm and has attempted just one pass. The other backups are Jack West and Jack Richardson. Last season, Richardson was the only healthy quarterback in spring ball.

• How will the offensive line be reshaped after a rough year for the unit?

Stanford spring football The first of two sessions comprise seven practices starting Tuesday and running through March 10. Where: Elliott Practice Field (behind Maples Pavilion) Open practices: 2-4 p.m. Saturday; 1:15-3:15 p.m. Sunday,; 12:15-1:45 p.m. March 9; 12:45-2:45 p.m. March 10

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Despite the loss of four starters, there’s plenty of promise here. Drew Dalman got plenty of work at center last season when starter Jesse Burkett was recovering from an injury. Guard/tackle Foster Sarell and tackle Walker Little were the two highest-rated O-line prospects coming out of high school in 2017. Guard Devery Hamilton has plenty of experience, and guard Dylan Powell played during the late stages of 2018.

The line, however, had big problems carving out holes in the running game under first-year coach Kevin Carberry. The Cardinal ranked 11th in the Pac-12 in rushing yards per game and in yards per carry.

• Who will replace Arcega-Whiteside (school-record-tying 14 TD catches) as the go-to receiver in the red zone?

The most likely candidate is 6-foot-7 tight end Colby Parkinson, although there are plenty of promising wide receivers. Among them are Connor Wedington and Donald Stewart (both coming off injury-shortened seasons), Michael Wilson, Osiris St. Brown and Simi Fehoko. Plus, heralded freshmen Elijah Higgins and Colby Bowman join the team in August.

• Will Cameron Scarlett be a 1,200-yard tailback, or will Stanford use a tailback-by-committee?

Returnees Trevor Speights and Dorian Maddox will be in the running, as will current freshman Justus Woods and incoming freshmen Austin Jones (Bishop O’Dowd-Oakland) and Nathaniel Peat. Much depends on the answer to question No. 2.

• Who will start at inside linebacker?

Okereke, the team’s leading tackler, is headed to the NFL, and the other starter, Sean Barton, retired from football. That leaves a group of unproven players, led probably by freshmen Ricky Miezan and Jacob Mangum-Farrar, although Curtis Robinson (two games last season) has been shifted from the outside for his final season.

Tom FitzGerald is a San Francisco Chronicle staff writer. Email: tfitzgerald@sfchronicle.com Twitter: @tomgfitzgerald