Player form v attributes

Hi. I have a low ranked LM who is weak across the board for attributes. He’s not much good in other comps but in the league he performs - in fact he is top of the entire league’s list of player ratings. Is this a fluke? Should I keep him in ahead of a seemingly much better player? I ask as I’m going against strong opp and it feels wrong to further weaken my team’s quality against them. Thanks in advance, Dan