Reyna was handed his first Bundesliga start against RB Leipzig on Saturday and earned his first assist in the competition by teeing up Haaland for the opener in a 2-0 victory.
That Gio/Erling connection though ⚡️⚽️ pic.twitter.com/4G92Ivezh5— Borussia Dortmund (@BlackYellow) June 20, 2020
Haaland doubled his tally in second-half stoppage time, ensuring Dortmund will finish the season as runners-up to Bayern Munich.
Asked for his thoughts about Reyna, the Norway international told bundesliga.com: "I called him the American Dream before and that's true.
"He's 17 years old and what he's doing on the pitch is amazing. He has a huge future in front of him."
Reyna said: "It was my first start, which I was really happy with. It was a big three points to secure second place, so we're all really happy."
Haaland has scored 13 goals in 14 Bundesliga games since arriving from Salzburg in January.
He has helped Dortmund set a new club record for goals scored in a single season, with Favre's men having found the back of the net 83 times in 33 games.
"We have a lot of good quality players and when we get to play good together we know we will create a lot of chances," said Haaland.
"It's an amazing win. We knew that Leipzig is a good team but we're also a good team.
"It's of course s*** that Bayern won, but that's how it is now and we have to make the best of it. Now we've secured second place and we'll try to get as close as we can to them."
Dortmund host Hoffenheim in their final game of the season next Saturday.