That is according The New York Times, citing U.S. intelligence and military officials.
As the US defense officials states, Russia has already sent almost 85% of its fielded army to fight in Ukraine. U.S. officials estimate that about 500 Russian troops are killed or wounded every day in Ukraine.
Read more: At Least Ten Generals Killed in Ukraine, Six Dismissed Due to Incompetence – British Intelligence

According to Seth G. Jones, the director of the international security program at the Center for Strategic and International Studies, such large losses significantly exhausted the Russian army and reduced the effectiveness of its actions on the battlefield.
“The Russian Army is seriously depleted. That has implications on their ability to fight an effective ground campaign in Ukraine,” he said, adding that Russians probably don’t have enough effective combat forces to even to fully take control of Donetsk region.
According to Evelyn Farkas, the director of the McCain Institute, the Russian authorities are taking every effort to attract new recruits for their army.

“They’re pulling people from all over. Unless they have a mass mobilization, which I don’t see them being able to do at this point politically, they’re going to be at a loss,” she said.
According to retired Gen. Philip M. Breedlove, who was NATO’s supreme allied commander for Europe, the Russian military has lost so many troops that in some cases units have tried to force captured Ukrainians to fight.
“They have a tremendous problem of manpower and an even tougher problem that the manpower they have is not well trained. Their best units have already been bloodied,” he said.

As Defense Express reported, More Than 26 Countries Contribute to $1.5 Billion of Military Assistance for Ukraine at Copenhagen Conference. We also wrote on Real russia’s Losses After Explosions at Saki Military Airfield in Crimea.
Read more: Eliminated Russian Commanders and Generals in Ukraine List (Live Updates)