Anthony Martial is out of Manchester United's opening Premier League fixture with a hamstring injury.
Martial scored three goals in five starts during United's pre-season schedule but sustained an injury in the 1-0 defeat to Atletico Madrid in Oslo on Saturday.
The Frenchman's absence could lead to Ten Hag starting Cristiano Ronaldo even though he missed the entirety of United's tour of Thailand and Australia and has only played 45 minutes in the last two months.
Read more: Ten Hag's verdict on United midfield
Anthony Elanga and Alejandro Garnacho are among the alternative options to play up front while Christian Eriksen is capable of playing on the right-hand side.
Jadon Sancho was unavailable for the Atletico friendly due to illness and has not been spotted in training pictures this week.
Ten Hag clarified signings Lisandro Martinez and Christian Eriksen are fit enough to start despite not being involved across the four games on tour.
United finished sixth last season and one of the lowest ebbs was the diabolical 4-0 defeat at Brighton in their penultimate game of the campaign.
"Our aim is to win every game," Ten Hag reiterated, "(that is) what Man United is standing for. We have to look forward to first game, our approach is to win every game, let's start Sunday.
"There is excitement in every season but you are coming in the season to a new club, a new team, we work really good and really tough in the last weeks, we're really looking forward to the start on Sunday.
"Brighton are a good team, decent football, attractive football. I like them."
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