We?ve now picked up 51 points (out of 57) from last 19 games.
Atletico got 50 from their first 19 games.
Our best runs during 19 games span (at any time during the season)
2008/09: 55 out of 57 points (from round 3 to round 22)
2010/11: 55 out of 57 (again from round 3 to Round 22, great consistency)
2012/13: 55 out of 57 (round 1 to 19)
Also worth mentioning other unbeaten runs:
2015/16: 51 out of 57 (round 8 to 26) - 16 wins, 3 draws
2017/18: 51 out of 57 (round 1 to 19) - 16 wins, 3 draws
2018/19: 49 out of 57 (round 14 to 32) - 15 wins, 4 draws
2016/17: 47 out of 57 (from 8 to 26) - 14 wins, 5 draws
For all the complains people here have on a daily base we've shown some great consistency in the league for most of the last decade.
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Honourable mentions:
Rijkaard's team picked up 51 out of 57 points from round 8 to round 26 in 2005/06 (after a relatively poor start of the season with 2 wins and 4 draws in first 7 games) but we've lost back to back games against Valencia and Atletico in February that year. Still won the league and CL in the end so nothing to complain about.
And in Rijkaard's first season (2003/04) we've also had a remarkable turnaround after New Year. We've had only 24 points after first 18 games and then doubled that amount in next 19 games. We went 17 games unbeaten (14 wins) before losing two of the last three but stil finished 2nd after starting calendar year as a midtable team.
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So we've had some good periods but besides the 2018/19 season we've usually had those winning/unbeaten runs at the start of the season (during Pep's and Tito's years) or starting in mid-October (after international break) at the latest (in Lucho's two years) not in December.
Another thing to mention is due to messed up schedule we've played teams like Bilbao and Elche twice during those last 19 games so it's not been an exact round trip playing against every team in the league. They've also changed rules before the 2019/20 season (IIRC) so opponents from rounds 20-38 doesn't repeat themselves in the same order as from rounds 1-19 (for example, first El Clasico has been played in Round 7 and second one will be played in Round 30 not in Round 26).
But you can only play who you have in front of you at the time the game is scheduled so clearly all of this doesn't diminish a turnaround Koeman and the team have done in last months.