The National Football League players who have worked to reach Super Bowl LII could be getting hit—not by their opponents, but by income taxes.

As millions of Americans prepare to tune in Feb. 4 as the New England Patriots take on the Philadelphia Eagles in Minneapolis, Minn., Bloomberg Tax analyzed the three highest paid athletes from each franchise to illustrate the tax burdens they face.

Those top-tier athletes like Tom Brady not only share the top U.S. income tax bracket, they also all face the unique complications presented by jock taxes, measured by the amount of duty days a player contributes to “income-related work” in any state that administers an income tax. Because the Patriots also made the Super Bowl in 2017, their duty days—and jock tax bills—are higher than the Eagles who missed out on last year’s postseason.

Sean Packard, tax director at Octagon Financial Services, told Bloomberg Tax that many players initially are surprised by their steep tax burdens.

“If we do our jobs educating them, they realize it is part of making a lot of money, even though they don’t like it,” Packard said.

New England Patriots

Each of the top paid Patriots takes home only 51.7 percent of his original salary:

• Stephon Gilmore (cornerback): $16.9 million salary, receives $8.74 million in net pay

• Tom Brady (quarterback): $15 million salary, receives $7.76 million in net pay

• Rob Gronkowski (tight end): $10.2 million salary, receives $5.28 million in net pay

Philadelphia Eagles

Each of the top paid Eagles receives only 53.5 percent of his original salary:

• Alshon Jeffery (wide receiver): $16 million salary, receives $8.56 million in net pay

• Fletcher Cox (defensive tackle): $9 million salary, receives $4.82 million in net pay

• Lane Johnson (offensive tackle): $7.98 million salary, receives $4.27 million in net pay

Federal, State Burdens

Packard said tax rates “sometimes” have an effect on the location in which players seek to work.

“It depends how much leverage a player has in negotiations,” he said. “It can be used as a way to get more money from a team in a high tax state.”

Just like any job, all athletes are subject to federal and state income taxes. For the 2017 regular season, all the NFL players analyzed fall into the top federal tax bracket of 39.6 percent, by far the biggest blow to their gross salaries.

However, under the 2017 federal tax act (Pub. L. No. 115-97), players only will be subject to 37 percent federal income tax for income earned beginning in 2018.

Athletes also are subject to state income tax rates, which vary by state. In Massachusetts, where the Patriots’ Gillette Stadium is located, the state income tax rate is 5.1 percent. However, on Feb. 6 the Massachusetts Supreme Judicial Court will hear oral arguments over whether voters can consider on the November ballot a millionaire’s tax—which would impose an additional 4 percent surcharge on incomes over $1 million.

In the Eagles’ home state of Pennsylvania, the state income tax rate is 3.07 percent.

Jock Taxes, Other Burdens

Professional athletes also are subject to a jock tax calculated by the amount of days a player contributes to “income-related work” in any state that administers an income tax.

Days spent in foreign jurisdictions are called “duty days” and are counted on the first day of NFL open practice by every state except Arizona and Michigan—which begin counting duty days on the first day of the regular season, according to Packard.

For away games, each team spends at least two days in the state, translating to two duty days. The two duty days are divided by the annual total of duty days. Because the Patriots played into 2017 last season, and won the Super Bowl in the process, they have duty days that roll over, bringing their total to 196 and allowing states to tax 1.02 percent of a player’s salary.

The Eagles, who didn’t make the playoffs last year, have a duty day total of 160, which allows states to tax 1.25 percent of a player’s total salary.

Players also face an agent fee, which averages around 3 percent of a player’s salary, Packard said. High-income individuals making more than $200,000 are also subject to a 0.9 percent Medicare surplus tax.

Financial Planning

Ryan Losi, financial adviser and executive vice president at PIASCIK, an accounting firm that works with athletes, told Bloomberg Tax that players should take advantage of the league’s financial advising program to help them stay aware of their amassing tax burden. The program is paid for in part by union dues—$10,000 taken from each players salary.

Packard said players should always be asking questions.

Players should “talk to their accountants and financial advisers, and ask all the questions they have until they understand how much they are paying and why,” he said.