Danny Cowley got most of his January transfer deals completed early in the window.
Hayden Carter, Tyler Walker, Ollie Webber and Denver Hume arrived throughout the month, while Aiden O’Brien was added to the squad on deadline day.
Meanwhile, several players who had not featured much in the first half of the season departed the club.
And Cowley is pleased with the options he can call upon for the remainder of the campaign, starting with this weekend’s trip to Oxford.
The Blues boss said: “When the team isn’t winning, there’s going to be some disappointment, criticism and negativity – we understand that.
“A lot’s been made about the players who left us in January, but you look at how many games they contributed.
“It was only Lee Brown and John Marquis who had a significant number, while the boys who have come in are already starting matches.
“We may be quite small in number at the moment, but I believe that we’re high in quality and will only see the positives.
"When the team isn’t winning, there’s going to be some disappointment, criticism and negativity – we understand that."
“I really believe in this group and another boost for us is that Ryan Tunnicliffe is back on the grass and moving much freer.
“He looked like he had a lot of trust in his hamstring and he trained again with us on Thursday, so it’s a really big plus for us – it’s like a new signing in itself.
“With the athleticism and power he possesses, we know that he can really add a lot to our midfield department.”
Pompey will look to get back on track when they face League One’s sixth-placed side at the Kassam Stadium on Saturday.
Cowley said: “Oxford are a very good team, particularly in possession. I watched them against AFC Wimbledon recently and they were outstanding.
“They played through their opponents and got around them, while they get numbers in the box and carry a real offensive threat.
“I also saw Oxford more recently against Gillingham and they had total control, while they were awarded four penalties – I don’t think I’ve ever seen that before.
“Against Wigan on Tuesday, they had to show the other side of their game and really dug in. It was a feisty affair and I anticipate a tough test at the weekend.”