Instead, he believes Pompey’s players should be solely targeted following their abject previous two outings.
Whittingham has been blasted by fans in some quarters after overseeing successful dreadful displays against Newport and AFC Wimbledon.
Those defeats saw the club dumped out of the Johnstone’s Paint Trophy and hovering around 16th spot in the League Two table.
The manner of the losses have ignited plenty of anger among supporters who demand complete effort from their players.
Austrian Ertl skippered Pompey in the Dons disaster before being substituted in the 56th minute when the scoreline was 1-0. The visitors eventually slumped to a 4-0 loss – the third time they have conceded four goals in a match this season.
Ertl can understand fans’ frustrations but doesn’t believe some should be rounding on Whittingham.
He said: ‘I think it is quite harsh to criticise the manager.
‘Let’s be a little bit realistic here, we have a completely new set-up, a new club, everybody works so hard and it’s down to us players.
‘Every one of the staff are doing a great job here. They live for Pompey and you can’t ask for more.
‘It is down to us players that we do our jobs properly. We have got to learn from it as a team – that is the most important thing.
‘The players should be criticised, not the manager, it is down to us.
‘We have got to sit down, analyse it, look at what went wrong and where we can improve, but it is definitely down to us because we are prepared as good as possible.
‘Guy is brilliant. He lives for Pompey. You cannot ask for more as a manager.
‘He knows this place inside out – but it is down to us players to respond and just show what we can do for this club.’
Although currently sitting 16th, League Two remains congested in the rush for promotion and play-off spots.
Pompey are currently six points away from seventh place – the final play-off position.
They also have a game in hand following the abandonment against Wycombe at Fratton Park last month.
Regardless, the past two performances have been unquestionably dreadful, with a total of seven goals conceded and none scored.
Ertl added: ‘We are big fish in a small pond. It doesn’t make life easy for us to be fair and expectations are rising, rising, rising.
‘We have got to be realistic where we are. There is a budget for mid-table but expectations are very high.
‘But we have still got to work hard. We had a good run in the league before and can do that again – no doubt about that.
‘Everybody is together and we must move on again.’