The phrase "was a considerable blow" is correct and usable in written English.
You can use it to describe a situation in which someone experiences a strong negative event or setback, such as the loss of a job, the end of a relationship, or a financial hardship. Example: The news that the company was closing down operations was a considerable blow for the employees.
This was a considerable blow.
Aleksandr Zheleznyakov, a scientist with the Federation of Russian Cosmonautics, said the latest mishap was "a considerable blow to the industry's image, particularly taking into account our many setbacks in the last couple of years".
So it was a considerable blow to the parties of the ruling coalition that in a public letter this week, more than 140 senior doctors denounced them as having left health services in the worst state of the NHS's 67-year existence.
The loss of Agüero is a considerable blow to City and Pep Guardiola.
With continuing doubts about Rio Ferdinand's fitness, losing Vidic, who has been an outstanding performer since joining from Spartak Moscow in 2006, would be a considerable blow.
Losing Yoann Huget is a considerable blow but Philippe Saint-André made 13 changes to the side that beat Italy, demonstrating the strength at his disposal.
A decision by the Shiites to move ahead without the Sunnis would be a considerable blow to efforts by the Bush administration to bring the leaders of the Sunni minority into the negotiations over the constitution.
Still, it would be a considerable blow given that there are still a number of months between now and then, depending on when it takes effect.
If the injury is serious, it would be a considerable blow to the Angels bullpen.
Meanwhile, in less pleasing news for the Blues, the Londoners have been handed a considerable blow to their long-term transfer strategy after Atletico Madrid forward Antoine Griezmann announced his plans to remain in Spain.
Jose Mourinho has been dealt a considerable blow to his January transfer window plans after Inter Milan sporting director Piero Ausilio revealed that the San Siro club have no intention of selling Fredy Guarin.
