As others have noted, HYG can often be used an indicator for market turning points both to the downside and upside. In reviewing all significant pullbacks since Dec-2012 this seems to hold true. Of 8 occurrences looked 6 occurrences had HYG bottom before the S&P. 2 occurrences showed them to bottom on the same day. Average length for SPY to mark a low after HYG was 3 days with 6 days being the largest.
HYG and SPY are both sitting near long term support lines. HYG bounced off theirs on Monday. SPY touched the support line yesterday. It should be noted that HYG did not make a new high like SPY did (2007 top in SPY showed same divergence). Watching HYG's bounce off its support line may give some clues to whether more weakness is ahead. A new downtrend line may be developing in HYG and if it can not be cleared this may cause problems.