Bayern Munich scored three goals after the 84th minute to cap a 5-4 victory over RB Leipzig.
RB briefly kept Bayern off the top of the Bundesliga for three weeks last November with a transfer policy of signing raw, young talent - all five signings in the a year ago are 21 or younger. Naturally we expect more of him with his qualities, but it is not easy for a young player to adjust to a new country, a new style of play.
But Costa will feel as though he's shown enough to be worthy of a regular starting spot at an elite club, and given Juventus lack a natural left-sided winger, he would surely see a lot of game time in Turin if the transfer went ahead.
Bayern boss Carlo Ancelotti called the match an "absolutely insane game".
"We're used to playing very structured football, plenty of possession, compact and aggressive defending".
And Leipzig - who ran them pretty close at one point earlier in the year - remain second in the table, but a whole 13 points behind their lofty opponents.
The World-Cup victor would be a good acquisition for Mauricio Pochettino as he would be solid in a back three defensive line-up that the Spurs manager has been favouring for much of this campaign.
"Nevertheless, Leipzig showed they deserve to be up where they are".
Ralph Hasenhüttl (RB Leipzig coach): "Congratulations to FC Bayern on an incredible victory".
Robert Lewandowski calmly restored parity from the spot on 17 minutes, before Leipzig retook the lead with a penalty of their own from Timo Werner.
Second-placed Leipzig capped their first year in Germany's top flight by qualifying directly for next season's Champions League while Saturday's visitors Bayern are already confirmed as German champions. Both sides have achiched their goal for this Bundesliga campaign.
To further highlight just how good Bayern usually are at the back, the four goals they conceded today against Leipzig accounts for 19% of the goals they have conceded in the league this season. For a long time we seemed to be winning against the best German team that oozed quality.
Danish striker Yussuf Poulsen netted Leipzig's third on 47 minutes when his shot wrong-footed Bayern's third-choice goalkeeper Tom Starke after clipping Alonso's boot. Questions will be asked of Bayern's defence, which shipped four goals for the first time since losing 4-1 at Wolfsburg in January 2015.