Denard Span is a clear upgrade over Lombardozzi.
He's top 10 amongst CFers in WAR, OBP, DRS and UZR. His OPS is .720 which is better than Lombardozzi's. It's better than Lombo's split against righties even.
Span is a clear upgrade. Oh and he hits .278/.340/.380 in the leadoff spot, compared to Lombo's .248/.295/.322
Lombardozzi is a temporary player. When Werth returns, it's not a sure thing that we want Span playing over Morse, Harper, or Werth. Morse is making contact and earned the benefit of the doubt with his performance last year. Harper is the future. Jayson Werth was hitting well (OPS+ of 121) before his injury. Span just isn't a big enough difference maker to shove any of those guys to the bench.
If we decided to move LaRoche (which I would disgaree with), then yes bring on Span. At this point we don't have the prospects to trade for a guy who would possibly just be place-holding until Werth gets back in the lineup, which should be August.