Thomas Tuchel has revealed he is quite frustrated with how Dortmund failed to get the second goal and drew 1-1 at Mainz.
Reus scored the opener early in the game after Andre Schurrle set him up and they created good chances to double the lead.
Unfortunately, Dortmund could not get the second goal and fell to an equaliser from Danny Latza with seven minutes left to play.
“It was a decent away game from our side in the opening 45 minutes,” Tuchel stated at a news conference.
“But we were unfortunately not able to make the most of our dominance and score a second. It is annoying. We failed to double our lead.
“We did not give away any chances of note until the equaliser. I think we were very alert in defence and showed the right attitude. We dealt well with their counterattacks.
“We feel that we should have had a few more points now. It will be difficult.”
Dortmund remain fourth in the Bundesliga table following this weekend’s results, trailing table-topping Bayern Munich by 14 points.