I don't know that his pace was terrible.
These days there is so much going on (like conserving the tires, where he is conserving fuel so he could push later on, etc...).
The thing is that he is racing against Alonso, and that's who you are fighting with.
There is basically no driver who has beaten him (don't want to start any Hamilton thing here).
So your reputation will always be connected to how you fare against Alonso (the same is true offcourse for the other star drivers).
But I don't know a driver who is so complete and has so little offdays (and there we go again with the praise, lol).
Stoffel has to nail perfect weekends (no horrible starts, no 0.5sec of Alonso in quali and taking every opportunity thrown at you).
When he can do that he will be more then fine, if he can do that we will see.
Today he made a great recovery race but it could have been so much more.