(This story is for CNBC Pro subscribers only.) Jefferies slashed its rating on Tesla to hold in a late Monday call as the electric automaker's monster rally this year pushed its valuation to unsustainable levels. The bank downgraded Tesla to hold from buy after the stock surged nearly 100% year to date. The sudden jump in the stock raised concerns it had become a speculative bubble and become detached from fundamentals. "However convinced we are about the Tesla equity opportunity, we still need valuation to be grounded into some visibility on market size and potential profitability," Jefferies analyst Philippe Houchois said in a note to investors on Monday. "Plugs should be grounded." Shares of Tesla skyrocketed, surpassing $900 a piece earlier this month, driven partly by a short squeeze and a strong quarterly earnings as well as an upbeat outlook. The company also announced a $2 billion common stock offering , taking advantage of its surging stock price to raise more capital. The rally took a pause lately after the company warned the coronavirus outbreak may cause damage to its business. It mentioned "health epidemics" to its risk factors for the first time, noting that the coronavirus may cause Tesla to "incur expenses or delays relating to such events outside of our control." Tesla shares fell 7% to $833.79 during Monday's market rout.