Keeper Alex Cisak and striker Jake Jervis yesterday arrived on loan to bolster Blues numbers.
They join Ricardo Rocha at Fratton Park, who penned an initial month-long deal earlier in the week.
During a hectic end to the emergency loan window yesterday, attempts to also recruit a midfielder failed.
That relied on one of Pompey’s fringe players successfully leaving on loan, although the clock beat all those concerned.
In addition, a switch to Port Vale for Jed Wallace didn’t materialise.
Nonetheless, Whittingham is delighted with the three arrivals in the past week.
Pompey now find themselves with options in attack and in the centre of defence.
And the caretaker manager believes that competition can boost performances in the battle against relegation.
He said: ‘Competition for places makes players play better, without a doubt.
‘I have been in the situation where you look on the sideline or start the game thinking “if I don’t do well here I am going to get dragged?”
‘The competition all over the pitch now is fantastic.
‘We have got some up front now which, for me, is the most important area – scoring goals.
‘We had the same problem with centre-halves but, with Ricardo coming in, now we have got three of them.
‘There is always one on the bench looking to get in and we need that everywhere.’
The News revealed Pompey’s interest in Cisak earlier in the week. The 23-year-old keeper was a regular for Oldham last season. But contractual issues have kept him out of their side since mid-September.
Jervis netted for Carlisle in the 4-2 defeat of Pompey earlier in the campaign.
The Birmingham youngster has also spent time on loan at Tranmere this season.
Whittingham added: ‘Alex is a keeper who likes to control his area and dominate. That is so helpful to a back four, they know where they stand.
‘He communicates really well, whether he is organising the balance of the team or coming for crosses.
‘He’s also very experienced at this level and, by all accounts, is a very hard worker as well.
‘With Jake, from the accounts of all the players that played against him, he gave one of the better performances from a striker they have faced this season.
‘He is somebody who can get the ball down and play, somebody not scared to run the channels as well.
‘I think he gives us something different. Izale (McLeod) likes getting in behind and playing on shoulders, Paul (Benson) can be the other way around – a decent a target man and get involved in build-up play.
‘Jake does a bit of both, which is ideal for us.’