After the worst first-half for U.S. stocks in decades, a major rebound last week prompted some optimism that the worst of the sell-off may be behind us — but not everyone's convinced . It's perhaps unsurprising that market watchers are reluctant to call the bottom on the brutal selloff, but there's one indicator that many strategists say is key: earnings revisions. Trevor Greetham, head of multi-asset at Royal London Asset Management, says an "earnings recession" is coming, which he expects to "drag on for quite a long time." "Earnings are the next problem … This rally could persist a bit longer, but don't think this is the end of the bear market," told CNBC's "Squawk Box Europe" on Monday. Morgan Stanley is also keeping a close watch on earnings revisions. "Equity markets tend to trough 2-3 weeks before earnings revisions bottom, however the latter have not even turned negative yet," Morgan Stanley's European strategists, led by Graham Secker, noted on Monday. In a separate note on U.S. equities, the bank noted that the bounce in the S & P 500 last week was due to valuations moving higher — an "unusual" phenomenon given the growing concern about earnings. "Falling yields and lower oil prices have lowered the terminal rate for the Fed. Whether this is bullish or bearish depends on one's interpretation. Last week, the market took the bullish view which may last a few more weeks before the reality of lower earnings arrives and the bear market resumes," strategist Michael Wilson said. Read more With recession fears surging, UBS dips into the history books to predict what could happen These global stocks look oversold — and analysts are expecting a rebound Goldman Sachs analysts reveal some of the most 'attractive' stocks as recession fears mount Secker noted that while the MSCI Europe may be in the later stages of a valuation de-rating, the peak-to-trough price decline still looks quite modest relative to prior downturns. This is due to earnings estimates which have continued to rise year-to-date despite the sharp fall in equity prices, Secker explained. "We do not expect this divergence to last much longer however and see a high chance that the economic news flow deteriorates over the next couple of months, which should put downward pressure on [gross domestic product] and [earnings per share] forecasts," he added. How low can earnings go? In a note entitled "Earnings: how low can they go?" UBS also stresses the importance of earnings, although it take a slightly more optimistic tone. "With the S & P 500 P/E down [around] 6x YTD, how much earnings will fall is a key debate," the bank's strategists, led by Keith Parker, wrote last week. It added that its baseline scenario for the U.S. is "slowing growth but no recession." The bank forecasts earnings per share (EPS) of $235.50 and $250 for the S & P 500 for 2022 and 2023, respectively, which they believe are "achievable." This compares to $186.60 in 2021, according to FactSet data. However, the strategists stressed that "risks are to the downside." The bank has an "implied EPS change indicator" which it says remains positive, pointing to further upgrades. "S & P 500 implied revisions over the next 8wk remains positive. Energy, Utilities and REITs have the highest sector level implied EPS revisions. Transportation and Banks lead IGs [investment grade]," the analysts wrote. The bank said its indicator had been a "helpful signal" during periods of market weakness and earnings downgrades, including the stock market crash of 2008 to 2009.