Here is where Marner ranks among Leafs forwards for on ice impact at ES:
Shots for: 1st for totals, 4th/60
Scoring Chances for: 2nd for totals, 3rd/60
High Danger Chances for: tied for 3rd for totals, 9th/60
xGoals for: 1st for totals, 5th/60
Goals: 1st for totals, 2nd/60
High Danger rate would be the thing to look at to support your argument here.
Getting to the lines, Keefe appears to be less worried about forward ES matchups against the Point line and more about making sure McCabe and/or Brodie is out there against them,
As far as forwards go there are 6 forwards between around 17-19 minutes against Point so far and Marner is one of them.
Marner's numbers against Point at even strength so far:
TOI: 17:13
Corsi: 64.86% (24-13 Marner)
Shots: 60.00% (12-8 Marner)
Scoring Chances: 68.75% (11-5 Marner)
High Danger Chances: 100.00% (5-0 Marner)
xGF%: 68.92% (Highest xGF% of any forward against Point)
GF%: 100.00% (2-0 Marner)