One of Wall Street's biggest stock market bulls is lowering his year-end target on the S&P 500.

Morgan Stanley's Chief U.S. Equity Strategist told The Halftime Report today that he's cutting cutting his year-end S&P 500 target by 5%.

"I only see 3%-4% earnings growth for the S&P this year, which represents a 16x multiple and by that calculation, the S&P 500 only gets to 2,050 this year," said Parker.

Parker says there are real risks out there. He's watching the Chinese economy and the U.S. Dollar.

"It's harder to be that optimistic when you have a stronger dollar, lower oil, and lower economic outlook," added Parker.

"I'm setting up my portfolio thinking about three buckets," said Parker.

"Defensives, growth and the unknown area which is financials and energy. You have to overweight and underweight a little bit in each area to avoid taking on too much risk," he adds.

Morgan Stanley now lies at the lower range of Wall Street estimates for the S&P 500 this year. Their 2,050 target represents about 1% upside from today's closing.