Doubts are growing over the viability of this season's county competitions as clubs face increasing difficulty putting out sides.

ESPNcricinfo understands that the combination of Covid-related withdrawals and Hundred call-ups has decimated county squads with Kent, for example, now without their first-choice 17 players.

The ECB have already announced the cancellation of Derbyshire's final two T20 Blast fixtures. The club have been hit by a spate of injuries and Covid withdrawals leading to a situation where 20 of their players are currently unavailable. The club and ECB subsequently concluded they were unable to put out a team that could "maintain the integrity... of the competition."

Several other first-class counties have cancelled their List A matches against the National County sides which were scheduled for next week leading to increasing doubts over whether the Royal London One-Day Cup will even be able to go ahead.

Even before Covid hit, several county squads had been hit hard by Hundred call-ups, with Surrey losing a dozen players. With the ECB desperate to ensure their new competition goes ahead, there are concerns that any further calls upon county squads will undermine the credibility of the 50-over domestic competition to extent where it is abandoned for a second year in succession.

There is also a three-day match next week between a county XI and the India touring squad which will be used as a warm-up to the Test series against England which starts on August 4.

Clubs are also understood to be struggling with stewarding, with at least one of them considering playing games behind closed doors. In several cases, the numbers of trained staff - especially stewards - has been limited by the requirement to self-isolate.

While the counties seem keen to play - not least to satisfy their membership which has witnessed very little cricket over the last 18-months - there is unease about the quality of the product which may be on display at time. There will also be searching questions of the ECB about the sustainability of four formats and the wisdom of pressing on with a new competition during a pandemic.

"We're determined to play the Royal London One-Day Cup," Neil Snowball, the Managing Director of County Cricket, told ESPNcricinfo. "It's an important competition to us.

"There was always a process by which Hundred sides could take players from counties in the case of injury. It might be that is utilised for illness or to comply with Covid protocols, too.

"If we do have another outbreak, we could reduce the number of games. But there's no plan to change the groups.

"It's a very challenging time, there's no doubt about it, and clubs do have some concerns. But everyone involved is adamant they want to play."

The ECB on Wednesday confirmed that Derbyshire Falcons' final two Vitality Blast group-stage matches have been cancelled.

"ECB has determined that Derbyshire CCC is unable to field a team of a strength appropriate to maintain the integrity of the two matches and of the competition as a whole," it said in a statement.

"Derbyshire are adhering to Covid-19 protocols and managing a number of injuries. In addition to six injured players, 14 members of Derbyshire's squad are self-isolating after they were deemed as close contacts of an unnamed team-mate, who tested positive for Covid-19 earlier this week."

Derbyshire were due to play Northamptonshire Steelbacks on Friday and Yorkshire Vikings on Sunday.

"Those matches will be deemed as having been cancelled," the ECB statement continued. "Under Playing Condition 16.11.4.5 the North Group will, therefore, be decided on an 'average points per completed match' basis."

Northamptonshire announced that Friday night's fixture at The County Ground would be replaced by an exhibition T20 match featuring two Steelbacks sides led by Josh Cobb and Graeme White.

"All existing eTickets claimed by Season Ticket Holders and Life Members remain valid and will carry over to the new event," a Northamptonshire club statement said.

"In the case of Derbyshire, the Competition Management Group met and went through the process of hearing whether they could put out a team," Snowball continued. "They really couldn't, so the decision was taken to cancel the games."

The ECB also confirmed that the LV= Insurance County Championship match between Derbyshire and Essex, abandoned earlier this week, would be treated as a draw. Both teams have been awarded eight points plus the bonus points they had accrued before the match was abandoned, giving Essex a total of 11 points and Derbyshire nine.

George Dobell is a senior correspondent at ESPNcricinfo