Brentford boss Thomas Frank admits David Raya is on his way to Arsenal.
The Spain goalkeeper is set to join the Gunners on an initial season-long loann.
Frank confirmed: "I expect [David Raya's] deal will be completed with Arsenal. He's not here at the moment and won't be involved on Sunday.
"Mark Flekken was one of the best keepers in the Bundesliga last year. I like his personality; he is a leader.
"I like his distribution and dominance in the area. From the first game in America to Lille, he has got better each time."