Don't ask Jose Quintana about the Cubs' first-half problems. All they've done since acquiring him from the White Sox is win.
This 6-0 run for the Cubs since the Quintana trade is exactly what a president of baseball operations or a general manager hopes will happen when they make a trade.
Theo Epstein made a tough call -- dealing two of his top prospects in a four-player package to the White Sox -- and it has paid immediate dividends. Will the Brewers' David Stearns, the Cardinals' John Mozeliak or the Pirates' Neal Huntington make a move to answer?
That's one of the questions on the table as teams in the newly tightened National League Central race head into the weekend.
Would adding Sonny Gray or another starting pitcher help turn things around for the Brewers? They've lost five in a row and watched their lead over the Cubs shrink from 5 1/2 games to only one.
The Cardinals and Pirates have also gained ground in the last week. Will that move them off the bubble into the ranks of buyers?
Both teams are trying to extend the postseason window for core groups of players who have done great things. But the Pirates only reached .500 on Thursday and the Cardinals are still under .500.
As for the Cubs, they probably aren't done adding parts. They are still rumored to be following the starting-pitching market and are definitely candidates to add a bullpen arm or a veteran catcher to provide insurance behind Willson Contreras.
With the Cardinals at Wrigley Field, the Brewers in Philadelphia and the Pirates in Colorado, the picture could get clearer this weekend.
Among the on-field questions in play:
• CanJacob ArrietaandJonathan Lesterkeep the Cubs rolling?
This is a weekend of great matchups at Wrigley. The Cardinals have top gun Carlos Martinez lined up to face Arrieta on Friday and future franchise Hall of Famer Adam Wainwright on track to go against Lester on Saturday.
Arrieta seems ready to put a disappointing first half behind him. His velocity was up a little last Saturday in Baltimore, which shows he's not blustering about feeling great and expecting big things in August and September. Lester breezed through Monday's start in Atlanta after getting shelled by the Pirates on the eve of the All-Star break.

Wainwright vs. Lester brings back memories of the 2013 World Series, when Lester carried Boston to its championship with victories in Games 1 and 5 over Wainwright. They also met in Lester's first start for the Cubs, with Wainwright winning the 2015 opener at Wrigley.
• How will Quintana's welcome to Wrigley go?
Quintana was given his first ice-water shower in a Cubs victory party in Baltimore, but Sunday night will be his first chance to boogie in the Cubs' party room. The lefty is sure to get a huge ovation from fans when he goes to the mound, as he announced his arrival with seven shutout innings against the Orioles. He faces Michael Wacha, who was overpowering in a 119-pitch shutout of the Mets on Tuesday.
• How will the health ofRyan BraunandKristopher Bryantimpact the race?
Braun has been in and out of the Milwaukee lineup all season, and he was limited to pinch-hit duties in Thursday's game by soreness in both his wrist and calf. The situation isn't considered serious but it comes at a bad time for the Crew, as Eric Thames (7-for-25 in the second half, with no home runs to offset 13 strikeouts) and Keon Broxton (1-for-15) haven't been providing offense like they did in the first half.
Bryant badly scared Joe Maddon and Cubs Nation when he exited Wednesday's victory in Atlanta with an injury to his left hand after a headfirst slide into third base. X-rays showed that he only sprained his pinkie, which caused him to predict a speedy return. The Cubs probably won't rush him back as they're firing on all cylinders (44 runs, 16 home runs and a .985 OPS in six games since the All-Star break).

• Will the Phillies help out the teams chasing the Crew?
Three games at Citizens Bank Park sounds like a good thing, but the Brewers will need to pitch well to have a good weekend on their way to Washington. The Phillies are swinging the bat, especially Odubel Herrera (.333, two homers, 1.179 OPS in the second half) and rookie Nick Williams (.360, two homers, 11 RBIs and a 1.197 OPS). The Brewers just took two of three against the Phillies at Miller Park, which will be fresh in both teams' memory banks.
•Tommy Pham, an unexpected key for the Cardinals?
The erstwhile fourth outfielder/Memphis Redbird has been a lifesaver for the Cardinals. He's been one of the best hitters in baseball lately, going 11-for-29 with two homers since the All-Star break. That's a continuation of his good work since joining the team May 5 (.309/.392/.532).

Good for him. He waited a long time for his chance and is making the most of it. As far as hot goes, the Cubs' answer to Pham is Javier Baez, who has gone 10-for-20 with two homers since the break.
• Can the Pirates keep rolling in Colorado?
The Bucs have won their last four series, going 11-3 to move from seven games back to only three. But it's going to take some really good pitching and defense to make it five winning series in a row.
No team in the Major Leagues is hitting the ball like the Rockies, who have scored nine runs or more in six of their last nine games, including 18 against the Padres on Wednesday. Nolan Arenado had three homers in that game, but Charlie Blackmon (.403 with six homers in July) and Gerardo Parra (.556 OBP, with a 1.425 OPS and only one strikeout since the break) have been equally productive.