Catch up on today's top five analyst downgrades with this list compiled by The Fly: 1. Petrobras (PBR) downgraded to Neutral from Buy at UBS with analyst Luiz Carvalho citing reduced visibility on its long-term pricing policy after the company recently reduced prices, which significantly lowered the chances of the company selling its refining assets, keeping it a monopoly, and exposed it to possible interference depending on the government's policy approach and macro conditions. 2. Domino's Pizza (DPZ) downgraded to Hold from Buy at Maxim with analyst Stephen Anderson saying the company's comp performance and market share gains in the U.S., accelerated unit development worldwide, and mostly favorable cost outlook warrant a premium multiple, but believes these positives have been priced into shares. 3. Noble Energy (NBL) downgraded to Hold from Buy at Tudor Pickering. 4. Sientra (SIEN) downgraded to Hold from Buy at Maxim with analyst Anthony Vendetti saying that while he is optimistic on Sientra's long-term prospects, the valuation is significantly ahead of peer averages and the stock price has exceeded his 12-month target. 5. Quanex (NX) downgraded to Neutral from Buy at Sidoti. This list is just a portion of The Fly's full analyst coverage. To see The Fly's full Street Research coverage, click here.