I'm a little fuzzy on how MLB views constantly calling up and sending down a player to limit their service time, but I see three possible scenarios for Nelson... First, Polanco was called up on June 10th to avoid Super 2. Nelson has 32 more service days than Polanco so that puts his "safe" call up date at July 12th. Now this just happens to coincide with an Estrada match-up against the Cardinals. Would be a perfect time for Nelson to come up. The second option is to create a little buffer but only have Estrada pitch one additional game. Estrada pitches July 12th, the all-star break happens July 14-17, the Brewers pitch their top 4 in the rotation after the all-star break with Estrada pitching out of the pen and call up Nelson to pitch July 22nd against the Reds. Adds an additional 10 day service time buffer and we only have 1 additional Estrada start. The third option, and the league and players association may frown on this due to messing with a player's service time to their detriment, is call Nelson up for the start on the 12th, send him down, and then call him up for good to start on the 22nd.