The Jets were walloped 4-0 by Melbourne City on Saturday night, leaving them with one win for the season and in the box seat to claim the wooden spoon.
It's been a particularly tumultuous time for the club since 28 January, when captain Kew Jaliens was one of five players sacked.
Jaliens was then signed by City and scored against his old side on the weekend.
Stubbins paid tribute to the way his charges had toiled over the past six weeks, but added that the club's lack of depth had been shown up by City.
"We need to recognise without the real quality and depth that is needed at the club, it's a hard task to keep backing up week after week after week," Stubbins said.
"They've got Aaron Mooy and Robert Koren in the middle of the park there and Josh Kennedy is up front.
"With all respect to what we've got at the club, we need to invest in a way that we can get ourselves some parity in the contest."
Stubbins noted there was a "lot of work going on behind the scenes" in that regard.
"We need to do things in a way that there's a real diligence surrounding who we bring to the football club," he said.
"The advantage for us is we've got quite a lengthy period now before we can finalise a squad for the coming campaign."
Stubbins was confident that would take place in both the short and long term, starting with the Jets' clash against Western Sydney Wanderers on Saturday.
The fixture at Parramatta will go a long way to decide who takes home the wooden spoon.
"We've got six games to go. There's a lot of things on the players' minds," Stubbins said.
"Is it contracts? Is it fatigue?
"We had a bad day at the office. We'll regroup and go again."
Stubbins suggested there was no animosity between the club and Jaliens and City coach John van 't Schip agreed.
"He moved on. He knows that's part of football," van 't Schip said.
"He loves Newcastle... his family is still living there."
