Ever since the Champions Trophy 2017, Pakistan's bowling line-up has seen to go down in numbers and the performance. The spin department and the fast bowling unit have not been up to their full potential lately.
Pakistani spinners average 43.6 since the Champions Trophy. Their strike-rate is 54.4 whereas the economy rate is 4.80 which is the third best after Afghanistan and Bangladesh.
Pakistan needs its spin department to fire in the ICC Cricket World Cup 2019. That is the only way they can pick wickets in the middle and stop the run flow. Otherwise, it will be problems for Sarfraz Ahmad in negotiating its bowlers in the middle.