Sanderson and Co were eventually bowled out for 445 on day one, and they then set about getting stuck into their visitors.
Middlesex struggled with the bat on Saturday and closed on 134 for seven from 46 overs, with Jason Holder, Nathan Buck and Luke Wood all taking two wickets apiece.
Sanderson also managed a dismissal.
And the bowler said: “We know we’re capable of this type of performance but putting two days together like this is what we’ve been trying to do for the past two seasons.
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“We’ve been known to collapse the morning after a good day but we got stuck in again and got their bowlers coming back for third-fourth spells.
“There’s so much less pressure with runs on the board - you can bowl a bit fuller knowing it’s not a disaster if you get driven.
“Hopefully we can step on the gas tomorrow and get them back in again.”
Middlesex have a mountain to climb in the opening clash of the Specsavers County Championship Division Two season.
And bowler Steven Finn said: “It’s been a tough couple of days. Personally it's nice to be back playing with no injury worries at all and to get through unscathed is really good.
“We bowled some good spells but didn’t dovetail it together but fair play to their guys who played well.
"A trait of ours for a long time has been getting out of sticky situations and this is a true test of this now."