NEW YORK -- Nolan Patrick is week to week for the Philadelphia Flyers and will not be able to start the season at the 2019 NHL Global Series.

The forward has a migraine disorder, and Flyers general manager Chuck Fletcher said they haven't decided if he will be placaed on injured reserve or long-term injured reserve.

"He's taking the medication now and we're hoping that settles down the migraines and gets him to feeling 100 percent from a health perspective," Fletcher said Thursday prior to a preseason game at the New York Rangers. "After that, he's skated a bit but he's essentially missed all of training camp. He hasn't played games. He hasn't been in any battle drills. We're going to have to make sure we get him the conditioning work he needs. Hopefully by the time we get back from Europe we'll have a better sense of where he's at from a health perspective and after that if it's all going well it's just a matter of conditioning."

Philadelphia opens the season Oct. 4 against the Chicago Blackhawks in Prague. The Flyers leave Friday for Switzerland, where they will play against National League team Lausanne on Monday, and Patrick will not be on the trip.

Fletcher said Patrick notified the Flyers in June that he was experiencing headaches. They worked with Patrick throughout the offseason to try to get to the root of the problem, consulting various medical experts, including a neurologist. They were concerned because the headaches came on randomly.

"That was the confusing part of it from a medical perspective, but we consulted a lot of different people and I think we feel we're in a good place medically," Fletcher said. "We'll hope for the best."

Fletcher said the 21-year-old has a history of migraines from when he was younger. He said there is also a family history of migraines and added that the doctors do not believe the headaches to be concussion-related.

"At this point I think he feels relieved to know what it is," Fletcher said. "The doctor feels that there's a regimen he can put him on with medication so we can control the situation and we're hopeful."

Patrick had 31 points (13 goals, 18 assists) in 72 games last season. The No. 2 pick in the 2017 NHL Draft, behind Nico Hischier of the New Jersey Devils, has 61 points (26 goals, 35 assists) in 145 NHL games.