A second man was jailed and former Minnesota Gophers quarterback Philip Nelson was cut from the Rutgers football team Tuesday, both for their alleged roles in a scuffle that turned ugly last weekend in Mankato.

Assault charges are expected to be filed Wednesday against Trevor Shelley, 21, who authorities and witnesses say punched Isaac Kolstad, rendering him unconscious on a street outside bars that had just closed early Sunday.

Kolstad, 24, remains in critical condition following his latest surgery Tuesday morning stemming from a fractured skull, brain swelling and severe lung problems caused by a lack of oxygen. The surgery at a Mayo Clinic facility in Mankato went well, according to his family’s CaringBridge site.

Nelson, a ballyhooed quarterback from Mankato, started several games for the Gophers the last two seasons before transferring to Rutgers recently. He was expected to sit out next fall, an NCAA transfer requirement, and then play in 2015 and 2016. His legal troubles following the alleged assault have now scuttled those plans.

Rutgers coach Kyle Flood, in a statement announcing his release, said his team’s “thoughts and prayers are with Isaac Kolstad and his family.”

Mankato police said tips led to Shelley’s arrest. Using video from city surveillance cameras, authorities released images of a man running from the scene in a torn red shirt. Shelley was arrested at his home in St. Peter on Monday night, four hours after police released the videos.

Nelson posted $20,000 bail to get out of the Blue Earth County jail Monday after facing first- and third-degree assault charges for allegedly kicking a defenseless and unconscious Kolstad in the head. The criminal complaint against Nelson refers to an unknown male in a red shirt punching Kolstad, who “immediately goes limp and collapses on the pavement.”

“Mr. Shelley was the individual we were looking for in the red shirt,” said Todd Martin, Mankato’s public safety director. “We contacted him and then went to his residence and made the arrest.”

Charges expected Wednesday

Shelley is expected to be charged with the same two counts of assault as Nelson and make a first appearance in Blue Earth County District Court on Wednesday morning.

Unlike Nelson, who has no criminal history, Shelley has a legal background that includes convictions for underage drinking and driving, taking a vehicle without permission and driving on a suspended license.

Shelley’s Facebook page lists his high school as Mankato West, the same school where Nelson, 20, became a star quarterback. Nelson told police he didn’t know the man who punched Kolstad. Shelley wasn’t a football player like Nelson or Kolstad, who played for Minnesota State, Mankato.

Zach Buelow, who described Shelley as “one of my really good buddies,” said he’s shocked by the allegations. “He doesn’t seem like a fighter,” Buelow said.

Buelow said Shelley moved out to Colorado last year and worked, but he came back after about six months. Since then, he’s been employed full time putting up drywall, the friend added.

According to the criminal complaint, a heated verbal argument began — possibly involving a bouncer who kissed the hand of Nelson’s girlfriend earlier in the evening. Some people told police that Nelson might have confused Kolstad with the bouncer.

After exchanging words, Kolstad struck Nelson in the back with a punch, knocking Nelson and another man to the ground, according to the complaint. Shelley then ran to the scene and delivered a punch that knocked Kolstad out cold before Nelson kicked the left side of Kolstad’s head as he lay sprawled and defenseless, according to authorities.

Miller said the occupants of a white vehicle seen in surveillance video have come forward and were interviewed by investigators. Police are still hoping other witnesses who saw the men before the altercation or observed what happened will come forward.