Pascal Bosschaart lauded Feyenoord's mentality as his players responded to a turbulent period with a memorable Champions League upset of AC Milan.

Feyenoord qualified for the last-16 stage of the competition for the first time in their history after Tuesday's 1-1 draw at San Siro secured a 2-1 aggregate victory.

Their former forward Santiago Gimenez levelled the tie for Milan – who lost the first leg 1-0 – after just a minute but Julian Carranza's second-half header sent the visitors through.

Brian Priske was dismissed just two days before the opening meeting in the play-off tie, though interim boss Bosschaart says this result was a perfect response to criticism.

"This says about the team that they have character. I think that's what I'm most proud of," Bosschaart told Ziggo Sport.

"You have to remember that they come from a very difficult phase, have received a lot of criticism, a change of coach, and then an unknown person comes in front of the group who occasionally throws in some empty slogans.

"That is a very difficult phase for them but I do think we are very clear, very transparent and very honest and this group responds very well to it, so I am proud of it."

Bosschaart's side got off to a terrible start as Gimenez, who scored five times in as many European games for Feyenoord this season, became the first player to score for and against the same team in a single Champions League campaign.

Gimenez's opener just 36 seconds in was Milan's third fastest from the start of a Champions League game, after Clarence Seedorf vs Schalke in September 2005 (21 seconds) and Alexandre Pato vs Barcelona in September 2011 (24 seconds).

The Eredivisie side's plight was then aided by Theo Hernandez's 51st-minute dismissal, however, with the Milan defender shown a second caution for simulation.

"If you concede a goal within minutes, the plan you wanted to execute will be different again," Bosschaart added.

"Everyone will now say that we took the upper hand after the red card but I also thought in the first half that we played quite well. Only after the red card it might be a little easier."

Feyenoord could still return to San Siro in the next round, where they will face either Inter or Arsenal, but for now Bosschaart needs to let their achievement sink in.

"It's beautiful. We are one round further, so very special," Bosschaart continued.

"It's fantastic but I have to say, it hasn't really landed with me yet."